U.S. patent application number 15/445792 was filed with the patent office on 2017-09-28 for duplex projectile cartridge and method for assembling subsonic cartridges for use with gas-operated firearms.
The applicant listed for this patent is SUPERIOR SHOOTING SYSTEMS, INC. (TX Corp.). Invention is credited to G. David TUBB, George Wyatt Tubb.
Application Number | 20170276463 15/445792 |
Document ID | / |
Family ID | 55955235 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170276463 |
Kind Code |
A1 |
TUBB; G. David ; et
al. |
September 28, 2017 |
Duplex Projectile Cartridge and Method for Assembling Subsonic
Cartridges for use with Gas-Operated Firearms
Abstract
A duplex projectile cartridge system (e.g., 400) for use in a
standard rifle (e.g., 10) has a front bullet (e.g., 320) and a
substantially cylindrical back bullet (e.g., 440) coaxially aligned
with one another. The front bullet's base is held in the cartridge
case neck far enough to engage the back bullet's front surface so
that the case neck simultaneously bears upon the front bullet and
the back bullet. Optionally, the cartridge configuration orients
the back bullet and defines one or more gas bypass lumens to allow
expanding gas to initially bypass the back bullet and drive the
front bullet distally to force an inter-bullet gap (e.g., "IBG"
480) upon firing.
Inventors: |
TUBB; G. David; (Canadian,
TX) ; Tubb; George Wyatt; (San Antonio, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUPERIOR SHOOTING SYSTEMS, INC. (TX Corp.) |
Canadian |
TX |
US |
|
|
Family ID: |
55955235 |
Appl. No.: |
15/445792 |
Filed: |
February 28, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2015/047618 |
Aug 29, 2015 |
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15445792 |
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62044175 |
Aug 29, 2014 |
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62104987 |
Jan 19, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B 5/025 20130101;
F42B 33/001 20130101; F42B 5/067 20130101; F42B 12/34 20130101;
F42B 5/03 20130101 |
International
Class: |
F42B 5/03 20060101
F42B005/03; F42B 5/02 20060101 F42B005/02; F42B 33/00 20060101
F42B033/00; F42B 5/067 20060101 F42B005/067; F42B 12/34 20060101
F42B012/34 |
Claims
1. A duplex projectile system (e.g., 100, 200, 300, 400, 500, 700)
for use in a standard military or tactical rifle system (e.g., 10)
of a selected caliber, comprising: (a) a cartridge case (e.g., 150)
with a substantially cylindrical body which is symmetrical about a
central axis extending from a substantially closed proximal head to
a substantially open distal mouth or lumen, where the body defines
an interior volume for containing and protecting a propellant
charge, and wherein the cartridge neck is configured to be
substantially cylindrical segment having a cylindrical interior
lumen in said selected caliber extending from the distal neck end
which defines the neck lumen, and wherein the cartridge neck lumen
has an interior sidewall with a selected axial neck length; and (b)
a front bullet and a back bullet coaxially aligned with one another
and with the case's central axis and held in the case neck (e.g.,
158) by inwardly squeezing force applied via the case neck, said
case neck squeezing force bearing simultaneously upon the front
bullet (e.g., 120) and the back bullet (e.g., 140).
2. The duplex projectile system of claim 1, wherein said front
bullet (e.g., 120, 220) has a body with a tapered or contoured
ogive terminating distally in a tip, and wherein said front bullet
body has a proximal or rearward portion with a rear cylindrical
sidewall segment terminating proximally in a tapered sidewall
segment which then transitions to a rearwardly projecting
frustoconical boat tail (e.g., 126, 226) which is symmetrically
defined around the front bullet body's central axis, and the
frustoconical boat tail terminates proximally or rearwardly in a
substantially planar transverse rear end or surface configured to
be received snugly within a front cavity of the back bullet (e.g.,
140, 240).
3. The duplex projectile system of claim 2, wherein said front
bullet (e.g., 120, 220) has an open distal tip which defines a
front facing cavity or opening symmetrically defined around the
bullet's central axis,
4. The duplex projectile system of claim 2, wherein said back
bullet (e.g., 140, 240) is configured with a full caliber sidewall
having distal open tip (e.g., 142, 242) and lacking the
conventional rounded or tapered nose and terminates at the front
(or distally) in a very wide full caliber distal or front-facing
concavity which defines a front facing opening symmetrically
defined around the bullet's central axis, and that front facing
concavity is precisely configured to snugly receive, center and
support the rearwardly projecting frustoconical boat tail of the
coaxially aligned front bullet.
5. The duplex projectile system of claim 1, wherein said front
bullet (e.g., 320) has a body with a tapered or contoured ogive
terminating distally in a full metal jacket clad tip or an open tip
which defines a front facing cavity or opening where the front
bullet's body is symmetrically defined around the bullet's central
axis, and wherein said front bullet body has a proximal or rearward
portion with a rear cylindrical sidewall segment terminating
proximally in a substantially planar flat transverse base (e.g.,
328) which is symmetrically defined around the front bullet body's
central axis, and the front bullet's flat base provides a surface
configured to be received snugly against a front substantially
planar wadcutter surface (e.g., 342, 442, 542, 742) of the back
bullet (e.g., 340, 440, 540, 740).
6. The duplex projectile system of claim 4, wherein said back
bullet (e.g., 340) is configured with full caliber sidewall
extending from the distal or front substantially planar wadcutter
surface and symmetrically defined around the back bullet's central
axis, wherein the front facing substantially planar full caliber
wadcutter surface of the back bullet is precisely configured to
snugly receive and support the proximal flat base of the coaxially
aligned front bullet.
7. The duplex projectile system of claim 1, wherein said front
bullet is fabricated from lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass.
8. The duplex projectile system of claim 1, wherein said back
bullet is fabricated from lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass.
9. The duplex projectile system of claim 1, wherein cartridge case
is manufactured to one of (a) 7.62 NATO ammunition specifications,
(b) SS109/M855 5.56 NATO ammunition specifications or A191/MK 248
.300 Winchester magnum ammunition specifications.
10. A method for making a duplex projectile system for use in a
standard military or tactical rifle system in a selected caliber,
comprising the method steps of: (a) providing a cartridge case with
a substantially cylindrical body which is symmetrical about a
central axis extending from a substantially closed proximal head to
a substantially open distal mouth or lumen, where the body defines
an interior volume for containing and protecting a propellant
charge, and wherein the cartridge neck is configured to be
substantially cylindrical segment extending from the distal neck
end which defines the neck lumen rearwardly or proximally to an
angled shoulder segment which flares out to the cylindrical body
sidewall, and wherein the cartridge neck has a neck lumen interior
sidewall with a selected axial neck length; (b) providing a front
bullet with a rear or proximal surface of the selected caliber; (c)
providing a back bullet with substantially cylindrical full caliber
sidewall terminating in a distal front surface on one end and a
proximal base on the other end; (d) inserting a selected quantity
of a selected propellant or powder into the case's interior volume
through the cartridge case mouth; and (e) inserting the back
bullet's proximal base into the cartridge case mouth; (f) driving
the back bullet axially and down into the cartridge case's mouth so
that the back bullet's distal or forward front surface is recessed
into the cartridge case mouth and driven approximately half way
along the case neck sidewall's axial length so that about half the
case neck sidewall remains uncovered by the now inserted back
bullet, when looking into the cartridge case mouth.
11. The method for making a duplex projectile system of claim 10,
further comprising the steps of: (g) inserting the front bullet's
rear or proximal end into the cartridge case mouth; (h) driving the
front bullet axially and down into the cartridge case neck far
enough to engage or provide a selected gap from the back bullet's
distal front surface so that the case neck supports the rear of the
front bullet and the front of the rear bullet and coaxially aligns
the front bullet and the rear bullet with the case body's central
axis, thereby causing a substantially uniform case neck tension to
hold the front bullet and back bullet in the case neck by inwardly
squeezing force applied via the case neck simultaneously bearing
upon the front bullet and the back bullet.
12. The method for making a duplex projectile system of claim 11,
wherein said back bullet is driven into said case to expose
approximately 0.150 inches of case sidewall.
13. The method for making a duplex projectile system of claim 12,
wherein said front bullet is driven approximately 0.150 inches into
said case mouth to abut said back bullet's distal front surface,
while not driving said back bullet further into said cartridge
case's interior.
14. The method for making a duplex projectile system of claim 10,
(g) inserting the front bullet's rear or proximal end into the
cartridge case mouth; (h) driving the front bullet axially and down
into the cartridge case neck far enough to engage the back bullet's
proximal front meplat surface (e.g., 642) so that the case neck
supports the front bullet and drives the distal meplat of the back
bulled proximally and out of contact with the neck, thereby
defining an annular gas-bypass lumen between the cartridge and the
back bullet's distal meplat.
15. The method for making a duplex projectile system of claim 14,
wherein said annular gas-bypass lumen between the cartridge and the
back bullet's distal meplat has an outside diameter of 0.313 to
0.318 inches for a back bullet caliber of 0.308 inches.
16. A duplex projectile system for use in a standard military or
tactical rifle system of a selected caliber, comprising: (a) a
cartridge case with a substantially cylindrical body which is
symmetrical about a central axis extending from a substantially
closed proximal head to a substantially open distal mouth or lumen,
where the body defines an interior volume for containing and
protecting a propellant charge, and wherein the cartridge neck is
configured to be substantially cylindrical segment having a
cylindrical interior lumen in said selected caliber extending from
the distal neck end which defines the neck lumen rearwardly or
proximally to an angled shoulder segment which flares out to the
cylindrical body sidewall, and wherein the cartridge neck has a
neck lumen interior sidewall with a selected axial neck length; (b)
a front bullet and a back bullet coaxially aligned with one another
and with the case's central axis; and (c) wherein the duplex
projectile system is optimized to provide subsonic ammunition which
is adapted for use in a standard rifle equipped with a suppressor
or silencer.
17. The duplex projectile system of claim 16, wherein said front
and back bullets generate a higher gas pressure and when fired and
reach a selected subsonic velocity (e.g. 1050 fps) while
functioning in a standard rifle without requiring any adjustment to
rifle's gas system.
18. The duplex projectile system of claim 16, wherein said front
and back bullets are stabilized to provide consistent shot-to-shot
subsonic accuracy in a standard rifle's barrel.
19. The duplex projectile system of claim 18, wherein said front
and back bullets, are aligned and configured within said casing to
define at least one gas bypass lumen so that, when fired,
propellant gasses bypass the back bullet and pressurize the rear
surface or base (e.g., 328) of the front bullet (e.g., 320) which
is thereby forced into the rifle's barrel (e.g., 14) by said
bypassing gas; and wherein said back bullet is then driven into
said barrel thereby trapping said bypassing gas between said front
bullet and said back bullet, to provide an inter bullet gap (e.g.,
"IBG" 480) between said front bullet and said rear bullet; whereby
said front bullet and said rear bullet each engage the barrel's
rifling separately and independently, and each are individually
stabilized by the rifling.
20. The duplex projectile system of claim 16, wherein said back
bullet includes at least one longitudinal gas port defined between
the back bullet's sidewall and the back bullet's distal end; said
gas port being configured to allow expanding gas to pass distally
beside or through the back bullet's body and pressurize the space
behind the front bullet and drive the front bullet distally down
the firearm's bore; wherein said port is configured to direct said
gas to force an inter-bullet gap (e.g., "IBG" 480) between the
front bullet and the back bullet upon firing; and (d) wherein the
duplex projectile cartridge is optimized to provide subsonic
ammunition which is adapted for use in a standard rifle equipped
with a suppressor or silencer.
21. The duplex projectile system of claim 20, wherein said front
and back bullets generate a higher gas pressure and when fired and
reach a selected subsonic velocity (e.g. 1050 fps) while
functioning in a standard rifle without adjusting the gas
system.
22. The duplex projectile system of claim 21, wherein said front
and back bullets are stabilized to provide consistent shot-to-shot
subsonic accuracy in standard rifles.
23. The duplex projectile system of claim 22, wherein said front
bullet is fabricated from lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass.
24. The duplex projectile system of claim 22, wherein said back
bullet is fabricated from lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass.
25. The duplex projectile system of claim 16, wherein said
cartridge case is manufactured to one of (a) 7.62 NATO ammunition
specifications, (b) SS109/M855 5.56 NATO ammunition specifications
or A191/MK 248 .300 Winchester magnum ammunition specifications.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/US2015/47618, filed on Aug. 29, 2015, which
claims the benefit of U.S. provisional patent application No.
62/044,175, entitled Duplex Projectile System and Method, which was
filed on Aug. 29, 2014, and U.S. provisional application No.
62/104,987, entitled Duplex Projectile Cartridge and Method for
Assembling Subsonic and Supersonic Cartridges for use with
Gas-Operated Firearms, which was filed on Jan. 19, 2015, the entire
disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to ammunition used in firearms
and more particularly to ammunition for use with military or
tactical gas-operated semi-automatic or select fire rifles and
particularly ammunition intended for use in suppressor-equipped
gas-operated rifles.
BACKGROUND
[0003] Modern firearms such as rifles (e.g., 10, as shown in FIG.
1A) make use of cartridges that include a projectile seated in a
cartridge casing (as illustrated in FIGS. 1B and 1C). The casing
(e.g., 150) has an internal cavity defined therein that contains a
charge of rapidly combusting propellant or powder. A primer is
seated in a recess formed in a rear or proximal portion or proximal
of the casing. A hole in the casing places the primer in
communication with the internal cavity containing the powder. The
projectile is seated in the front or distal portion of the casing
such that the powder is more or less sealingly contained in the
casing between the primer and the projectile.
[0004] A firearm's action is used to fire the cartridge. For
example, the action can include a striker that carries a firing
pin. The action can be used to advance the cartridge into a firing
chamber ahead of firing. While in the firing chamber, a trigger
mechanism can be used to release a sear to cause the firing pin to
strike the primer, causing the primer to ignite. The primer's
ignition is directed to the powder, which burns within the casing.
The powder burns within the casing to generate a rapidly expanding
gas, which propels the projectile out of the casing and through the
barrel.
[0005] Modern gas-operated semi-automatic or select fire rifles
such as the M4, M16, AR-15, AR-10, XM-110 or SR-25 (e.g., rifle 10
as illustrated in FIG. 1A) are configured to shoot a variety of
types ammunition which are built to specified standards. For
example, the M118LR special ball cartridge illustrated in FIG. 1B
is designed to fire in gas-operated semi-automatic or select fire
rifles and will provide a specified ballistic performance in
standard rifles (e.g., AR-10 SR-25, XM-110, M14 or M21).
Suppressors (e.g., 12, as illustrated in FIG. 1A) are frequently
used by military and police marksmen and the incorporation of a
suppressor into a rifle system often changes the point of impact
for a given type of ammunition. The barrel and gas system for Rifle
10 are illustrated in FIG. 1E, and when the cartridge is chambered
and fired, the projectile or bullet 60 travels distally down the
bore and the pressurized gas from the ignited propellant behind the
bullet is communicated back into the action via a gas tube lumen
18. The addition or removal of a suppressor may change the
operating properties of a gas-operated semi-automatic or select
fire rifle, because more or less gas is fed back into the action,
and more gas may mean more force is applied to the bolt carrier
which controls bolt 20, thus changing the timing of unlocking,
extraction, ejection, buffering, loading and relocking (depending
on the characteristics of the rifle).
[0006] [Military marksmen, police marksmen and others who are
trained in using such standard or issued rifles have expectations
about how these rifles will function when using issued ammunition
and if those training expectations are unmet by a new rifle or
ammunition offering, the new offering will almost certainly be
rejected as unworkable. When the standard ammunition cycles
reliably in the standard rifle and shoots with acceptable precision
to a specified point of impact at a selected distance, that
reliable success defines the training expectations for the standard
rifle system (e.g., 10).
[0007] In certain operational environments, there is a desire for
ammunition which sends more than one projectile for each cartridge
fired, but the prior art attempts have all failed to meet the
established training expectations for users of the standard rifles.
A number of unusual ammunition configurations have been developed
for use by soldiers and military marksman, and several ammunition
developers have experimented with ammunition having two or more
projectiles (such as the Vietnam era's "M198" duplex or "salvo"
cartridge (MilSpec MIL-C-60131, as shown in FIG. 1D), which appears
to have been cancelled in 1980 as unworkable. There have been many
other multi-projectile ammunition configurations, but those have
all essentially required a new, non-standard firearm (such as
Winchester's multi-barrel "Salvo Rifle" prototype), and so have
been rejected as impracticable. Examples of patented
multi-projectile prototypes are illustrated in Robinson's
salvo-squeezebore ammunition (U.S. Pat. No. 3,450,050), Davies'
frangible shotshell (U.S. Pat. No. 6,257,147), and Eckstein's
composite flechette (U.S. Pat. No. 8,640,622). Many of these
multi-projectile ammunition prototypes were deliberately designed
to increase the "beaten zone" (or area imperiled with each shot)
and so deliberately achieved a wide scattered spread among
individual projectiles when firing salvos (as that term was used in
military musketry). This "salvo" design goal (i.e., a large beaten
zone) is very different from the precision rifle shooter's goal,
which is to carefully and accurately shoot into a small aiming
area, very repeatably. For these reasons, the prior art has not
provided an ammunition system which reliably and precisely provides
multiple hits on a small target and only on that small target.
[0008] There is a need, therefore, for a novel ammunition
configuration which provides the benefits of multiple projectiles
fired with each cartridge, but which does not frustrate the
training expectations for users of the standard rifles (with or
without suppressors), and does not create a "salvo effect" or
provide a dangerously enlarged and imprecise beaten zone around the
aim point or target. The subject matter claimed herein is not
limited to embodiments that solve any disadvantages or that operate
only in environments such as those described above. Rather, this
background is only provided to define relevant nomenclature and
illustrate one exemplary technology area where some examples
described herein may be practiced.
SUMMARY
[0009] The duplex projectile system and method of the present
invention provides an accurate and reliable novel ammunition
configuration which provides the fire superiority benefits of
multiple projectiles fired with each cartridge while preserving the
training expectations for users of the standard military or
tactical rifles (e.g., AR-10 SR-25, M14 or M21), and which also
provides precise, repeatable and accurate impacts on small targets
over selected engagement ranges, meaning the precision shooter can
fire two projectiles with each trigger squeeze and deliver accurate
hits on small targets while avoiding unintended hits on adjacent
objects or areas near the intended target.
[0010] The duplex projectile system of the present invention is
optimized to provide subsonic ammunition which is adapted for use
in a standard rifle (e.g., 10) equipped with a suppressor or
silencer (e.g., 12). "Subsonic" in this context means ammunition
which propels a projectile at a velocity intentionally selected to
be below the speed of sound (e.g., below 1126 feet per second (fps)
in dry air at about 70.degree. F. of slower than Mach 1), and
subsonic ammunition is usually selected for use with a suppressor
or silencer (e.g., 12) because the passing projectile won't
generate the supersonic "crack" noise heard by those in the
vicinity of a projectile having a velocity faster than the speed of
sound (e.g., more than 1126 fps in dry air at about 70.degree. F.
or faster than Mach 1). Briefly, that supersonic crack is created
when a supersonic projectile passes through the air and creates a
series of pressure waves in front of it, similar to the bow waves
created by a boat. These waves travel at the speed of sound, and
since the speed of the projectile is higher than those "bow" waves,
the waves are forced or compressed together to create a shock wave
which is audible as the supersonic crack which travels along the
trajectory of the passing projectile. When a gas operated rifle
(e.g. 10) is equipped with a suppressor (e.g., 12) and the shooter
wants to avoid making excessive noise, the shooter will typically
use subsonic ammunition which creates significantly less gas port
pressure than when firing standard (supersonic) ammunition. As
noted above, traditional subsonic ammunition often creates problems
in that the rifle's gas system may not cycle reliably, so a shooter
who doesn't want to modify the gas system of the rifle is required
to shoot the louder standard supersonic ammunition.
[0011] The subsonic embodiments of the duplex projectile cartridge
system of the present invention create significantly more pressure
at the gas port (e.g., 18) than standard single projectile subsonic
cartridges, thus allowing standard rifles (e.g., 10) to function
without requiring a gas system adjustment. This benefit is
important because the first and second bullets of the duplex system
of the present invention weigh more than any single bullet ever
manufactured for use in a standard service rifle (i.e., AR-10
SR-25, M14 or M21). The two bullets require a higher gas pressure
to reach the upper end of subsonic velocities (e.g. 1050 fps). This
higher gas pressure makes it possible for a user's standard rifle
to fire a subsonic load quietly and function without requiring
adjustment of the gas system. No other ammunition can provide
reliable gas system operation and consistent shot-to-shot subsonic
accuracy in standard rifles.
[0012] Significantly, this level of performance is achieved in part
because the barrels in standard rifles were discovered to provide
surprising stability for the first and second projectiles in the
duplex projectile system of the present invention. A standard rifle
(e.g., 10) typically has a barrel (e.g., 14) with rifling having a
twist rate of between one (360 degree) twist in ten inches to one
in twelve inches and is designed to stabilize a single projectile
of 147 grains to 175 grains travelling at the standard velocity
(e.g., 2650 fps-2800 fps). In the present invention, the front and
back bullets are each stabilized in that standard twist-rate rifle
barrel (e.g., 14 at subsonic velocity. The applicants have
discovered how to provide the enhanced terminal ballistic benefits
of firing a single long and heavy bullet at subsonic velocities,
but without requiring a different barrel; a single long bullet that
weighed the same amount as the duplex system's front and back
bullets would be too long to be stabilized in a standard twist-rate
rifle.
[0013] The duplex projectile system and method of the present
invention are specifically designed for use by trained users of
modern gas-operated semi-automatic or select fire standard rifles
(such as the rifle type illustrated in FIG. 1A) which are
configured to shoot a variety of types standard ammunition and
provide a specified ballistic performance in standard (e.g., M4,
AR-15, AR-10 SR-25, FN-FAL, M14 or M21) rifles. Suppressors are
frequently used by military and police marksmen and the
incorporation of a suppressor into a rifle system often changes the
point of impact for a given type of ammunition. The addition or
removal of a suppressor may also change the operating properties of
a gas-operated semi-automatic or select fire rifle, since more gas
is fed back into the action, and more gas means more force is
applied to the bolt carrier, thus changing the timing of unlocking,
extraction, ejection, buffering, loading and relocking (as noted
above).
[0014] As also noted above, military marksmen, police marksmen and
others who are trained in using such standard or issued rifles have
expended significant effort at great expense and so have well
established expectations about how these rifles will function when
using any issued ammunition, and those hard-earned training
expectations must be met by any new rifle or ammunition offering,
meaning that the new ammunition must cycle reliably in the
marksman's standard rifle and shoot with at least an acceptable
level of precision to a specified point of impact at a selected
distance.
[0015] The duplex projectile cartridge of the present invention
includes a duplex bullet assembly comprising a front bullet and a
back bullet which are carried in a cartridge case resembling the
cartridge case for the M118LR (7.62 NATO) cartridge (or case 150
for the M118 cartridge of FIGS. 1B and 1C). The case of the present
invention is substantially cylindrical and symmetrical about a
central axis 150A extending from the substantially closed proximal
rimless head to the substantially open distal or neck end and the
central case body defines an interior volume for receiving and
containing a propellant charge. In the completed assembly, the
front bullet and the back bullet are coaxially aligned with one
another and with the case's central axis and are held in the case's
neck by tensile force bearing upon the front bullet and the back
bullet. In the exemplary embodiment, the rimless case is made of
brass or steel and is manufactured to a standard configuration
(e.g., substantially identical to that used for the M118 cartridge
shown in FIGS. 1B and 1C).
[0016] The front bullet is preferably configured with an open tip
or a pointed conical polymer ballistic tip and is fabricated or
machined from one or more selected metals. The body of the front
bullet has a tapered or contoured ogive terminating distally in an
open tip which defines a front facing cavity or opening
symmetrically defined around the central axis, and the front facing
cavity may be configured to receive a polymer ballistic tip insert.
The diameter or "caliber" of the front bullet body is preferably
selected from among SAAMI standard calibers (e.g., nominally 0.308
inches or 7.62 mm) for use in a selected rifle (e.g., an FN-FAL,
AR-10, SR-25, M14 or M21). The central portion of the body of the
front bullet preferably includes a sidewall segment carrying a
plurality of circumferential grooves of shallow depth and spaced
longitudinally along the bullet sidewall from one another. The
proximal or rearward portion of the body of the front bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a tapered sidewall segment which then transitions to
a rearwardly projecting frustoconical "boat tail" which is
symmetrically defined around the front bullet body's central axis,
and the frustoconical boat tail terminates proximally or rearwardly
in a substantially planar transverse rear end or surface configured
to be received snugly within the front cavity of the back
bullet.
[0017] The back bullet is preferably configured with an open tip
and is fabricated or machined from one or more selected metals. The
largest outer diameter or "caliber" of the back bullet is
substantially identical to the front bullet body diameter (e.g.,
for the illustrative example, nominally 0.308 inches or 7.62 mm).
The body of the back bullet lacks the conventional rounded or
tapered nose and terminates at the front (or distally) in a very
wide distal or front-facing concavity which defines a front facing
opening symmetrically defined around the central axis, and that
front facing concavity is precisely configured to snugly receive,
center and support the rearwardly projecting frustoconical boat
tail of the coaxially aligned front bullet. The central portion of
the body of the back bullet preferably includes a sidewall segment
carrying a plurality of circumferential grooves of shallow uniform
depth but varying width and those circumferential grooves are
spaced longitudinally along the back bullet sidewall from the
distal or front end to the proximal or rear end. The proximal or
rearward portion of the body of the back bullet preferably has rear
cylindrical sidewall segment terminating proximally in a
substantially planar transverse rear end or surface which provides
a flat base back bullet configuration.
[0018] The method of assembling the duplex ammunition of this
embodiment is to provide a vertically oriented standard military
cartridge case which has been primed, insert a selected propellant
or powder charge into the case's interior volume through the
cartridge case mouth, insert a back bullet's proximal base into the
cartridge case mouth and drive the back bullet down into the
cartridge case's mouth so that the back bullet's distal or forward
edge is recessed into the cartridge case mouth and driven 150
thousandths of an inch into the case neck, such that approximately
150 thousandths of the case neck interior is uncovered by the now
inserted back bullet, when looking into the cartridge case mouth.
Next a front bullet's proximal boat-tail base is inserted into the
cartridge case mouth and the front bullet is driven down and seated
into the back bullet's open distal end or mouth so that the front
bullet's proximal boat-tail is received in and centered by the rear
bullet's distal or forward surfaces when the front bullet is
recessed into the cartridge case mouth and driven 150 thousandths
of an inch into the case neck, so that once the duplex cartridge is
assembled, the case neck supports the rear of the front bullet and
the front of the rear bullet simultaneously.
[0019] In an alternative embodiment, the back bullet has a "wad
cutter" configuration. In this second embodiment, the front bullet
is preferably configured with a flat circular base and the body of
the front bullet has a tapered or contoured ogive terminating
distally in a distal solid tip or a front facing cavity or opening
symmetrically defined around the central axis, and the front facing
cavity may be configured to receive a polymer ballistic tip insert.
The diameter or "caliber" of the front bullet body is preferably
selected from among SAAMI standard calibers (e.g., nominally 0.308
inches or 7.62 mm) for use in a selected rifle (e.g., an FN-FAL,
AR-10, SR-25, M14 or M21). The central portion of the body of the
front bullet preferably includes a sidewall segment carrying a
plurality of circumferential grooves of shallow depth and spaced
longitudinally along the bullet sidewall from one another. The
proximal or rearward portion of the body of the front bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a transverse flat, circular base which is
symmetrically defined around the front bullet body's central axis,
and the substantially planar transverse rear flat base surface is
configured to abut a substantially planar "wad-cutter" front
surface of the back bullet.
[0020] The back "wad cutter" bullet is fabricated or machined from
a selected metal or is configured with a cladding metal jacket over
a lead core. The diameter or "caliber" of the back bullet is
substantially identical to the front bullet body diameter (e.g.,
for the illustrative example, nominally 0.308 inches or 7.62 mm).
The body of the back bullet lacks the conventional rounded or
tapered nose and terminates at the front (or distally) in a
full-diameter substantially planar and circular "wad-cutter" front
surface symmetrically defined around the central axis, and that
"wad-cutter"front surface is precisely configured to snugly abut
and support the flat base of the coaxially aligned front bullet.
The central portion of the body of the back bullet preferably
includes a sidewall segment carrying a plurality of knurled
sections or circumferential grooves of shallow uniform depth but
varying width and those circumferential grooves are spaced
longitudinally along the back bullet sidewall from the distal or
front end to the proximal or rear end. The proximal or rearward
portion of the body of the back bullet preferably has rear
cylindrical sidewall segment terminating proximally in a
substantially planar transverse rear end or surface which provides
a flat base back bullet configuration.
[0021] Another (third) embodiment includes a front bullet
configured with a flat circular base and the body of the front
bullet has a tapered or contoured ogive terminating distally in a
distal solid tip or a front facing cavity or opening symmetrically
defined around the central axis, and the front facing cavity may be
configured to receive a polymer ballistic tip insert. The diameter
or "caliber" of the front bullet body is preferably selected from
among SAAMI standard calibers (e.g., nominally 0.308 inches or 7.62
mm) for use in a selected rifle (e.g., an FN-FAL, AR-10, SR-25, M14
or M21). The central portion of the body of the front bullet
preferably includes a sidewall segment carrying a plurality of
circumferential grooves of shallow depth and spaced longitudinally
along the bullet sidewall from one another. The proximal or
rearward portion of the body of the front bullet preferably has
rear cylindrical sidewall segment terminating proximally in a
transverse flat, circular base which is symmetrically defined
around the front bullet body's central axis, and the substantially
planar transverse rear flat base surface is configured to abut a
substantially planar "wad-cutter" front surface of the back
bullet.
[0022] Another (fourth) embodiment provides a duplex projectile
system ammunition assembly and a surprisingly effective method for
creating separation between the first and second bullets within the
rifle's bore. Upon firing, the cartridge's ignited powder creates
an expanding gas bubble which initially urges both the front and
back bullets distally into the barrel's leade, where the front
bullet engraves itself on the rifling and begins to accelerate both
in its stabilizing rotation about the bullet's central axis and in
its travel distally down the bore toward the muzzle. The front
bullet is initially pushed by the back bullet. A plurality of ports
or longitudinal gas-ducting grooves or channels are defined in the
distal or forward portion of the back bullet to allow expanding gas
flowing distally into the barrel behind the distally moving front
bullet, to pressurize the base of the front bullet and force it
distally down the bore while the back bullet is moving slightly
more slowly, thereby creating an inter-bullet gap between the
distally forced accelerating front bullet and the distal or front
edge of the slower back bullet as both bullets travel distally down
the bore. This inter bullet gap defines a captive or trapped volume
of expanding gas between the front and back bullets as both travel
distally down the bore and allows each bullet to accelerate
independently. Within the barrel, each bullet is also independently
spin stabilized by the rifling, so the rifling twist rate need not
be optimized for a very, very long and heavy (e.g., 330 grains) and
instead a standard twist rate stabilizes each bullet
separately.
[0023] The above and still further features and advantages of the
present invention will become apparent upon consideration of the
following detailed description of a specific embodiment thereof,
particularly when taken in conjunction with the accompanying
drawings, wherein like reference numerals in the various figures
are utilized to designate like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1A and 1E illustrate the features and operation of a
contemporary standard military or tactical rifle system, (e.g.,
AR-10, SR-25 or XM-110) in accordance with the prior art.
[0025] FIGS. 1B and 1C illustrate a standard ammunition assembly
known officially as the M118LR 7.62 NATO cartridge, intended for
use in many standard military or tactical rifle systems (e.g.,
AR-10 SR-25, XM-110, FN-FAL, M14 or M21).
[0026] FIG. 1D illustrates another prior art ammunition assembly
intended for use in standard military or tactical rifle systems,
specifically the "M198" duplex or "salvo" cartridge (see, e.g.,
MilSpec MIL-C-60131).
[0027] FIGS. 2A and 2B illustrate a first embodiment of the duplex
projectile system ammunition assembly and method of the present
invention.
[0028] FIGS. 3A and 3B illustrate a second embodiment of the duplex
projectile system ammunition assembly and method of the present
invention.
[0029] FIGS. 4A, 4B and 4C illustrate the details of the front
projectile configured for use in the duplex projectile system
ammunition assembly and method of FIGS. 3A and 3B.
[0030] FIGS. 5A, 5B and 5C illustrate the details of an
alternative, lighter front projectile configured for use in the
duplex projectile system ammunition assembly and method of FIGS. 3A
and 3B.
[0031] FIGS. 6A, 6B and 6C illustrate the details of the rear
projectile configured for use in the duplex projectile system
ammunition assembly and method of FIGS. 3A and 3B.
[0032] FIGS. 7A, 7B and 7C illustrate the details of an
alternative, heavier rear projectile configured for use in the
duplex projectile system ammunition assembly and method of FIGS. 3A
and 3B.
[0033] FIGS. 8A and 8B illustrate, diagrammatically, plotted graphs
illustrating chamber pressure (in PSI) and velocity (in fps) as a
function of projectile travel distally down the bore of a rifle for
two embodiments of the duplex projectile system ammunition assembly
and method of the present invention and FIG. 8C provides a
comparable graph illustrating chamber pressure (in PSI) and
velocity (in fps) as a function of projectile travel distally down
the bore of a rifle for a single (well known) traditional
projectile.
[0034] FIGS. 9A, 9B, 9C and 9D illustrate another embodiment of the
duplex projectile system ammunition assembly and method of the
present invention.
[0035] FIGS. 9E, 9F, and 9G illustrate the on-target performance
for the duplex projectile system ammunition assembly and method of
the present invention.
[0036] FIGS. 10A, 10B, 10C, 10D, 10E and 10F illustrate another
embodiment of the duplex projectile system ammunition assembly and
method of assembling "gas bypass" duplex cartridge, in accordance
with the present invention.
[0037] FIGS. 11A, 11B, 11C and 11D illustrate an alternative
embodiment for the duplex projectile system ammunition assembly and
method for creating separation between the first and second
bullets, in accordance with the present invention.
[0038] FIGS. 12A, 12B, 12C, 12D, 12E, 12F and 12G illustrate a
preferred alternative embodiment for the duplex projectile system
ammunition assembly and method for creating separation between the
first and second bullets, in accordance with the present
invention.
[0039] FIGS. 13A, 13B, 13C and 13D illustrate another alternative
embodiment for the duplex projectile system ammunition assembly and
method for creating separation between the first and second
bullets, in accordance with the present invention.
[0040] FIGS. 14A and 14B illustrate another alternative embodiment
for the duplex projectile system ammunition assembly and method for
creating separation between the first and second bullets, in
accordance with the present invention.
DETAILED DESCRIPTION
[0041] FIGS. 2A-14B illustrate embodiments of the duplex projectile
ammunition assembly (e.g., 100, 200, 300, 500, 600, 700 and 800)
and methods for making and assembling selected components to
provide a surprisingly accurate and reliable ammunition system
which provides the fire superiority benefits of multiple
projectiles fired with each round while preserving the hard-earned
training expectations for users of the standard military or
tactical rifles (e.g., 10), and which also provides precise,
repeatable and accurate impacts on small targets over selected
engagement ranges. The duplex projectile system of the present
invention enables the precision shooter to fire two projectiles
with each trigger squeeze and deliver accurate hits on small
targets (e.g., the targets with 1/2 inch squares shown in FIGS.
9E-9G) while avoiding unintended hits on adjacent objects or areas
near the intended target.
[0042] Applicant's initial development work led to creation of the
first embodiment of the duplex projectile system and method of the
present invention, as illustrated in FIGS. 2A and 2B. Duplex
projectile system 100 is configured for use by trained users of
modern gas-operated semi-automatic or select fire standard rifles
(e.g., 10) which are configured to shoot a variety of standard
ammunition types and provide a specified ballistic performance in
standard rifles (e.g., AR-10 SR-25, XM-110, FN-FAL, M14 or M21).
Suppressors (e.g., 12) are frequently used by military and police
marksmen and the incorporation of a suppressor into a rifle system
typically changes the point of impact for a given type of
ammunition. As noted above, addition of suppressor 12 also changes
the operating properties of the rifle, because more gas is fed back
into the action, and more gas means more force is applied to the
bolt carrier, thus changing the timing of unlocking, extraction,
ejection, buffering, loading and relocking. As noted above,
military marksmen, police marksmen and others who are trained in
using standard issued rifles have been trained at great expense and
so have built-in expectations about how these rifles will function
when using any issued ammunition, and those training expectations
will be met by duplex projectile system 100 and cycle reliably in
the standard rifle 10 while shooting with surprisingly repeatable
precision to a specified point of aim (e.g., the 1/2 inch squares
shown in FIGS. 9E-9G) at a selected distance (e.g., 50 yards), as
discussed below.
[0043] Referring first to FIGS. 2A and 2B, duplex projectile
cartridge 100 includes a longitudinally, axially aligned two bullet
assembly comprising a front or distal projectile or bullet 120 and
a back or proximal projectile or bullet 140 which are carried in a
cartridge case 150 resembling the cartridge case for the M118LR
case of FIG. 1B. Cartridge case 150 is substantially cylindrical
and symmetrical about a central axis 150A (see FIG. 1C) extending
from the substantially closed proximal head 152 to the distal end
of neck 158 which defines substantially open lumen 154 and the
central case body defines an interior volume 156 for receiving,
containing and protecting a propellant charge 150F (not shown).
Cartridge head 152 has a substantially planar rear surface with a
central primer pocket 152P which is in communication with the
interior volume 156 via a flash-hole lumen, as is customary for
"boxer-primed" cartridge assemblies. The cartridge neck 158 is
substantially cylindrical and extends from the open distal neck end
which defines neck lumen 154 rearwardly or proximally to the angled
shoulder 150S which flares out to the substantially cylindrical
body sidewall 150SW, and the axial length of the cartridge neck 158
is preferably 0.310 inches and the axial length of the front and
back bullets 120, 140 is 2.260 inches, for the illustrated
example.
[0044] Front bullet 120 and the back bullet 140 are coaxially
aligned with one another and with the case's central axis 150A and
are held in case neck 158 by inwardly squeezing circumferential
force (or "neck tension") applied via the case neck 158
simultaneously bearing upon and supporting front bullet 120 and
back bullet 140, as shown in FIGS. 2A and 2B. In the illustrated
embodiment, rimless case 150 is substantially identical to the case
used for the M118LR cartridge illustrated in FIG. 1B but other
cartridge cases manufactured in conformance with 7.62 NATO
ammunition specifications (e.g., the M80 7.62 NATO case) may be
used in this exemplary embodiment. For ammunition in different
calibers (e.g., SS109/M855 5.56 NATO cartridges or A191/MK 248 .300
Winchester magnum cartridges), cartridge cases manufactured in
conformance with those respective ammunition specifications can be
adapted for use in the duplex ammunition system and method of
present invention.
[0045] Front bullet 120 is preferably configured with an open tip
122 or a pointed conical metal alloy or polymer ballistic tip (not
shown) and is fabricated or machined from one or more selected
metals (e.g., lead, tungsten, copper alloy cladded lead, copper
alloy cladded tungsten or C36000 brass). The body of the front
bullet has a tapered or contoured ogive terminating distally in
open tip 122 which defines a front facing cavity or opening
symmetrically defined around the bullet's central axis, and the
front facing cavity may be configured to receive a metal alloy or
polymer ballistic tip insert (not shown). The diameter or "caliber"
of the front bullet body is preferably selected from among SAAMI
standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use
in a selected rifle (e.g., 10). The central portion of the body of
the front bullet preferably includes a sidewall segment carrying a
plurality of distally projecting radial sidewall segments separated
by circumferential grooves of shallow depth (e.g., 14-24 one
thousandths of an inch) and spaced longitudinally along the bullet
sidewall from one another. The proximal or rearward portion of the
body of the front bullet preferably has rear cylindrical sidewall
segment terminating proximally in a tapered sidewall segment which
then transitions to a rearwardly projecting frustoconical boat tail
126 which is symmetrically defined around the front bullet body's
central axis, and the frustoconical boat tail terminates proximally
or rearwardly in a substantially planar transverse rear end or
surface 128 configured to be received snugly within a front cavity
of back bullet 140.
[0046] Back bullet 140 is preferably configured with a distal open
tip 142 and is fabricated or machined from one or more selected
metals (e.g., lead, tungsten, copper alloy cladded lead, copper
alloy cladded tungsten or C36000 brass). The diameter or "caliber"
of back bullet 140 is substantially identical to the front bullet
body diameter (e.g., for the illustrative example, nominally 0.308
inches or 7.62 mm). The body of back bullet 140 lacks the
conventional rounded or tapered ogive or nose and terminates at the
front (or distally) in a very wide distal or front-facing concavity
which defines a front facing opening 142 symmetrically defined
around the bullet's central axis, and that front facing concavity
142 is precisely configured to snugly receive, center and support
the rearwardly projecting frustoconical boat tail 126 of the
coaxially aligned front bullet 120.
[0047] The central portion of the body of the back bullet
preferably includes a sidewall segment carrying a plurality of
distally projecting radial sidewall segments separated by
circumferential grooves of shallow uniform depth (e.g., 14-24 one
thousandths of an inch) but varying width and those circumferential
grooves are spaced longitudinally along the back bullet sidewall
from the distal or front end to the proximal or rear end. The
proximal or rearward portion of the body of the back bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a substantially planar transverse rear end or base
surface 146 which provides a flat-base configuration for back
bullet 140. When front bullet boat tail 126 is seated within back
bullet cavity 142, there is a tapered annular gap of about 0.005
inches separating the outer diameter surface of front bullet boat
tail 126 from the interior surface of back bullet cavity 142, as
best seen in the enlarged detail view of FIG. 2B.
[0048] Alternative embodiments of the duplex cartridge system
(e.g., 200) and alternatives for the front bullet (e.g., 220, 220A)
and back bullet (e.g., 240, 240A) are illustrated in FIGS. 3A-7C.
Referring specifically to FIGS. 3A and 3B, duplex projectile
cartridge 200 includes a longitudinally, axially aligned two bullet
assembly comprising front bullet 220 and a back bullet 240 which
also have a combined axial length of 2.260 inches as carried in a
cartridge case 150. Front bullet 220 and back bullet 240 are
coaxially aligned with one another and with the case's central axis
and are held in case neck 158 by inwardly squeezing circumferential
tensile force (or "neck tension") applied via the case neck
simultaneously bearing upon and supporting front bullet 220 and
back bullet 240, as shown in FIGS. 3A and 3B. In the illustrated
embodiment, rimless case 150 is substantially identical to the case
used for the M118 cartridge illustrated in FIG. 1B, but other
cartridge cases manufactured in conformance with 7.62 NATO
ammunition specifications may be used. As in the prior embodiment,
front bullet 220 is preferably configured with a hexagonal-section
open tip 222 or a pointed conical metal alloy or polymer ballistic
tip (not shown) and is fabricated or machined from one or more
selected metals (e.g., lead, tungsten, copper alloy cladded lead,
copper alloy cladded tungsten or C36000 brass) preferably providing
a projectile weight of 175.7 grains.
[0049] Referring now to FIGS. 4A-4C, the body of the front bullet
220 has a tapered or contoured ogive terminating distally in open
tip 222 and the diameter or "caliber" of the front bullet body is
preferably selected from among SAAMI standard calibers (e.g.,
nominally 0.308 inches or 7.62 mm). The length of front bullet 220
is preferably 1.3 inches from the front or distal end (at opening
222) to base surface 228 (or about 4.22 times the caliber or
largest diameter) with the other dimensions as shown in FIGS. 4B
and 4C. The central portion of the body of the front bullet
preferably includes a sidewall segment carrying a plurality of
distally projecting radial sidewall segments separated by
circumferential grooves of shallow depth (e.g., 6-24 one
thousandths of an inch) and spaced longitudinally along the bullet
sidewall from one another. The proximal or rearward portion of the
body of the front bullet preferably has rear cylindrical sidewall
segment terminating proximally in a tapered sidewall segment which
then transitions to a rearwardly projecting frustoconical boat tail
226 which is symmetrically defined around the front bullet body's
central axis, and the frustoconical boat tail 226 terminates
proximally or rearwardly in a substantially planar transverse rear
end or surface 228 configured to be received snugly within front
cavity 242 of back bullet 240.
[0050] Back bullet 240 (see FIGS. 6A-6C and FIGS. 3A and 3B) is
preferably configured with a distal open tip 242 and is fabricated
or machined from one or more selected metals (e.g., lead, tungsten,
copper alloy cladded lead, copper alloy cladded tungsten or C36000
brass) to provide a preferred projectile weight of 161.7 grains.
The diameter or "caliber" of back bullet 240 is substantially
identical to the front bullet body diameter (e.g., for the
illustrative example, nominally 0.308 inches or 7.62 mm). The
length of back bullet 240 is preferably 1.3 inches from distal end
(at 242) to base surface 246 (or about 4.22 times the caliber or
largest diameter) with the other dimensions as shown in FIGS. 6B
and 6C. The body of back bullet 240 lacks the conventional rounded
or tapered ogive or nose and terminates at the front (or distally)
in a very wide distal or front-facing concavity which defines a
front facing opening or cavity 242 symmetrically defined around the
bullet's central axis, and that front facing concavity 242 is
precisely configured to snugly receive, center and support the
rearwardly projecting frustoconical boat tail 226 of the coaxially
aligned front bullet 220.
[0051] The central portion of the body of the back bullet
preferably includes a sidewall segment carrying a plurality of
distally projecting radial sidewall segments separated by
circumferential grooves of shallow uniform depth (e.g., 14-24 one
thousandths of an inch) but varying width and those circumferential
grooves are spaced longitudinally along the back bullet sidewall
from the distal or front end to the proximal or rear end 246. The
proximal or rearward portion of the body of the back bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a substantially planar transverse rear end or base
surface 246 which provides a flat-base configuration for back
bullet 240. When front bullet boat tail 226 is seated within back
bullet cavity 242, there is a tapered annular gap of about 0.005
inches separating the outer diameter surface of front bullet boat
tail 226 from the interior surface of back bullet cavity 242, as
best seen in the enlarged detail view of FIG. 3B.
[0052] Another embodiment of the duplex cartridge system (e.g.,
200) provides alternatives for the front bullet (e.g., 220A) and
back bullet (e.g., 240A) as illustrated in FIGS. 5A-5C and 7A-7C.
Referring specifically to FIGS. 5A-5C, the body of the front bullet
220A has a tapered or contoured ogive terminating distally in open
tip 222A and the diameter or "caliber" of the front bullet body is
preferably selected from among SAAMI standard calibers (e.g.,
nominally 0.308 inches or 7.62 mm), while providing a lighter
projectile weight of, preferably, 135.8 grains, due to fabrication
from lighter metal(s) than the front bullet embodiments described
above. The length of front bullet 220A is preferably 1.3 inches
from distal end (at opening 222A) to base surface 228A (or about
4.22 times the caliber or largest diameter) with the other
dimensions as shown in FIGS. 5B and 5C.
[0053] The central portion of the body of the front bullet
preferably includes a sidewall segment carrying a plurality of
distally projecting radial sidewall segments separated by
circumferential grooves of shallow depth (e.g., 6-24 one
thousandths of an inch) and spaced longitudinally along the bullet
sidewall from one another. The proximal or rearward portion of the
body of the front bullet preferably has rear cylindrical sidewall
segment terminating proximally in a tapered sidewall segment which
then transitions to a rearwardly projecting frustoconical boat tail
226A which is symmetrically defined around the front bullet body's
central axis, and the frustoconical boat tail 226A terminates
proximally or rearwardly in a substantially planar transverse rear
end or surface 228A configured to be received snugly within front
cavity 242 of back bullet 240B.
[0054] Back bullet 240B (see FIGS. 7A-7C) is preferably configured
with a distal open tip 242B and is fabricated or machined from one
or more selected metals (e.g., lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass) to provide a
heavier projectile weight of 209.3 grains. The diameter or
"caliber" of back bullet 240 is substantially identical to the
front bullet body diameter (e.g., for the illustrative example,
nominally 0.308 inches or 7.62 mm). The length of back bullet 240B
is preferably 1.3 inches from distal end (at opening 242) to base
surface 246 (or about 4.22 times the caliber or largest diameter)
with the other dimensions as shown in FIGS. 7B and 7C. The body of
back bullet 240B lacks the conventional rounded or tapered ogive or
nose and terminates at the front (or distally) in a very wide
distal or front-facing concavity which defines a front facing
opening or cavity 242B symmetrically defined around the bullet's
central axis, and that front facing concavity 242B is precisely
configured to snugly receive, center and support the rearwardly
projecting frustoconical boat tail 226A of the coaxially aligned
front bullet 220A. The central portion of the body of the back
bullet 240B preferably includes a sidewall segment carrying a
plurality of distally projecting radial sidewall segments separated
by circumferential grooves of shallow uniform depth (e.g., 14-24
one thousandths of an inch) but varying width and those
circumferential grooves are spaced longitudinally along the back
bullet sidewall from the distal or front end to the proximal or
rear end 246B. The proximal or rearward portion of the body of the
back bullet preferably has rear cylindrical sidewall segment
terminating proximally in a substantially planar transverse rear
end or base surface 246B which provides a flat-base configuration
for back bullet 240B. When front bullet boat tail 226A is seated
within back bullet cavity 242B, there is a tapered annular gap of
about 0.005 inches separating the outer diameter surface of front
bullet boat tail 226 from the interior surface of back bullet
cavity 242, as with the embodiment seen in the enlarged detail view
of FIG. 3B.
[0055] The method of assembling the duplex cartridge system (e.g.,
100 or 200) is to provide a vertically oriented standard military
cartridge case 150 which has been primed, insert a selected
propellant or powder charge (e.g., 160 or 260, such as Hodgdon
H4350 or H1000) into the case's interior volume through the
cartridge case mouth lumen (e.g., 154), insert a back bullet (e.g.,
140, 240, 240B) with the back bullet's proximal base into the
cartridge case mouth 154 and drive the back bullet axially and
proximally down into the cartridge case's mouth so that the back
bullet's distal or forward edge is recessed into the cartridge case
mouth and driven substantially half way down the neck, or one
hundred fifty thousandths of an inch into the case neck 158, such
that approximately half (or one hundred fifty thousandths) of the
case neck lumen's interior sidewall is uncovered by the now
inserted back bullet, when looking into the cartridge case mouth.
Next a front bullet (e.g., 120, 220 or 220A) proximal boat-tail
base is inserted into the cartridge case mouth 154 and the front
bullet is driven axially down or proximally and seated into the
back bullet's open distal end or mouth (e.g., 142) so that the
front bullet's proximal boat-tail (e.g., 126) is received in and
centered by the rear bullet's distal or forward surfaces when the
front bullet is recessed into the cartridge case mouth and driven
one hundred fifty thousandths of an inch into the case neck, so
that once the duplex cartridge system (e.g., 100 or 200) is
assembled, the case neck 158 supports the rear of the front bullet
and the front of the rear bullet simultaneously.
[0056] Testing of prototype duplex cartridge systems (e.g., 100 or
200) of the present invention for embodiments intended to generate
projectile velocities that are substantially subsonic or transonic
was confirmed with chronometer testing to confirm muzzle velocities
(e.g., the shots fired for the target shown in FIG. 9G were
measured at 1040 FPS). Computer modelling was used to confirm that
the duplex ammunition assembly of the present invention would
always generate a more than adequate amount of port pressure to
cycle a standard rifle's action (where standard rifles (e.g., 10)
typically require at least 10,500 PSI. An exemplary Military
Specification gas port pressure requirement is 12,500 psi+/-2000
psi (See, e.g., Mil-C-46934B for the M118 cartridge which specifies
gas port pressure for the M14 rifle). The Pressure-Velocity graphs
illustrated in FIGS. 8A and 8B show velocity (of the front or first
projectile) in the upper trace and pressure in the lower trace. The
pressure (lower) trace in FIG. 8A reflect chamber (and thus port)
pressure for a 295 grain duplex bullet assembly (e.g., 100, 200)
fired in a .308 Winchester SAAMI specification chamber (e.g., in
rifle 10) where the casing is charged with 19.8 grains of smokeless
powder propellant (e.g., 160 or 260, Hodgdon.TM. H4350). For the
example modelled in FIG. 8A, the front and back bullets were seated
into the neck to provide overall length ("OAL") of 2.80 inches.
This load, as modelled, generated chamber pressure data which
illustrates that the chamber pressure is initially over 15,000 PSI
and remains over 10,000 PSI as the duplex projectiles travel down
the bore (e.g., of rifle 10). FIG. 8B illustrates pressure vs.
projectile travel for duplex assembly 600 with a combined weight of
350 grains (as seen in FIGS. 12A-12G), where the casing is charged
with 23 grains of smokeless powder propellant (e.g., Hodgdon
H1000). FIG. 8C is provided here for comparison, illustrating
pressure vs. travel for a single 240 gr. Sierra.TM. subsonic
projectile (i.e., a 220 grain Sierra Match King.TM. bullet) for
comparison.
[0057] As noted above, to meet the normal (supersonic)
specification, the ammunition needs to supply 10,500 psi at the gas
port to reliably cycle the action. Referring back to FIG. 8B, the
pressure ported back into the action depends on the length of
barrel between the chamber and the port. "AR" style rifles (e.g.,
10) can have different length gas systems, so, as shown in FIG. 8B,
for a 350 gr Duplex cartridge assembly (e.g., 600) the Gas Port
Length vs. Chamber Pressure observations are: (a) Carbine=7
in.=10,500 psi, (b) Mid-length=9 in=8,800 psi and (c) Rifle=12
in=7,100 psi. In applicant's trials, each of these embodiments
worked, meaning that a standard rifle configured as rifle 10 is
configured generated adequate port pressure to reliably cycle.
Turning to FIG. 8C, for comparison, a 220 grain Sierra single
projectile load provides unreliable cycling, especially for a rifle
having a standard length gas system, due in part to Gas Port Length
vs. Chamber Pressure observations, which are: (a) Carbine=7
in.=7,100 psi, (b) Mid-length=9 in=6,000 psi, and (c) Rifle=12
in=5,000 psi. As a quick method for evaluating the internal
ballistics of these ammunition varieties in various rifles (e.g.,
10), we estimated that the chamber pressure is nearly equal to the
gas port pressure as the projectile passes the gas port lumen (so
that the gas port (e.g., 18) is pressurized. Duplex ammunition
(e.g., 600) theoretically meets the Mil Spec Requirement with a 7
in. long gas port, also other gas port lengths are close to the
required port pressure. Comparing the pressures from 350 gr. Duplex
load (e.g., 600, shown in Fig.) vs. the 220 gr Sierra single bullet
load, on average the duplex ammunition supplies about 45% more
pressure to the gas port 18. This is significantly more pressure,
and this difference in pressure at the gas port 18 explains why the
subsonic duplex ammunition assembly of the present invention (e.g.,
100, 200, 300, 400, 500, 600, 700, 800) is able to cycle many
standard semi-automatic firearms (e.g., 10) without any
modification to the firearm. It is understood that the gas port
pressure will differ slightly from the chamber pressure as plotted
in FIGS. 8A-8C, but applicant's development work and test results
from several trials indicate that the duplex bullet cartridge
assemblies of the present invention do cycle reliably in standard
issue rifles.
[0058] An alternative embodiment is illustrated in FIGS. 9A-9D,
where duplex cartridge system 300 includes a front bullet 320 which
is preferably configured as a spitzer with a flat circular base and
the body of front bullet 320 has a tapered or contoured ogive
terminating distally in a distal solid tip or a front facing open
tip or cavity or opening symmetrically defined around the central
axis, and the front facing cavity may be configured to receive a
polymer ballistic tip insert (not shown). The diameter or "caliber"
of the front bullet body is preferably selected from among SAAMI
standard calibers (e.g., nominally 0.308 inches or 7.62 mm) for use
in a selected rifle (e.g., 10). The central portion of the body of
front bullet 320 may optionally include a sidewall segment carrying
a plurality of circumferential grooves of shallow depth and spaced
longitudinally along the bullet sidewall from one another or a
knurled segment. The proximal or rearward portion 326 of the body
of the front bullet preferably has rear cylindrical sidewall
segment terminating proximally in a transverse flat, circular base
328 which is symmetrically defined around the front bullet body's
central axis, and the substantially planar transverse rear flat
base surface 328 is configured to abut a substantially planar
"wad-cutter" front surface of the back bullet 340, although an
inter-bullet gap may be defined therebetween or filled with an
optional wadding disc (not shown) of selected axial thickness
(e.g., 1 mm).
[0059] Front bullet 320 and back bullet 340 are coaxially aligned
with one another and with the case's central axis 150A and are held
in case neck 158 by inwardly squeezing circumferential force (or
"neck tension") applied via the case neck 158 simultaneously
bearing upon and supporting front bullet 320 and back bullet 340,
as shown in FIGS. 9A-C. In the illustrated embodiment for duplex
cartridge system 300, as with the prior embodiments, rimless case
150 is substantially identical to the case used for the M118LR
cartridge illustrated in FIG. 1B but other cartridge cases
manufactured in conformance with 7.62 NATO ammunition
specifications (e.g., the M80 7.62 NATO case) may be used in this
exemplary embodiment. For ammunition in different calibers (e.g.,
SS109/M855 5.56 NATO cartridges or A191/MK 248 .300 Winchester
magnum cartridges), cartridge cases manufactured in conformance
with those respective ammunition specifications can be adapted for
use in the duplex ammunition system and method of present
invention.
[0060] Back bullet 340 is fabricated or machined from a selected
metal or is configured with a cladding metal jacket over a lead
core. The diameter or "caliber" of the back bullet is substantially
identical to the front bullet body diameter (e.g., for the
illustrative example, nominally 0.308 inches or 7.62 mm). The body
of back bullet 340 lacks a conventional rounded or tapered nose and
terminates at the front (or distally) in a full-diameter
substantially planar "wad-cutter" front surface 342 symmetrically
defined around the bullet's central axis, and that "wad-cutter"
front surface 342 is preferably configured to snugly abut and
support the flat base 328 of the coaxially aligned front bullet
320, although an inter-bullet gap (see FIG. 9C) may be defined
therebetween or filled with an optional wadding disc (not shown).
The central portion of the body of the back bullet 340 optionally
includes a sidewall segment carrying a plurality of knurled
sections or circumferential grooves of shallow uniform depth but
varying width and those circumferential grooves are spaced
longitudinally along the back bullet sidewall from the distal or
front end 342 to the proximal or rear end. The proximal or rearward
portion of the body of the back bullet preferably has rear
cylindrical sidewall segment terminating proximally in a
substantially planar transverse rear end or surface which provides
a flat base. In the illustrated embodiment of duplex cartridge
system 300, rimless case 150 is substantially identical to the case
used for the M118LR cartridge illustrated in FIG. 1B, but other
cartridge cases manufactured in conformance with 7.62 NATO
ammunition specifications (e.g., the M80 7.62 NATO case) may be
used in this exemplary embodiment. For ammunition in different
calibers (e.g., SS109/M855 5.56 NATO cartridges or A191/MK 248 .300
Winchester magnum cartridges), cartridge cases manufactured in
conformance with those respective ammunition specifications can be
adapted for use in the duplex ammunition system and method of
present invention.
[0061] The method of assembling the duplex ammunition 300 of FIGS.
9A-9D is to provide a vertically oriented standard military
cartridge case 150 which has been primed, insert a selected
propellant or powder charge 360 (e.g., Hodgdon H4350 smokeless
powder) into the case's interior volume through the cartridge case
mouth 154, insert a back bullet's proximal base into the cartridge
case mouth and drive the back bullet 340 down into the cartridge
case's mouth so that the back bullet's distal or forward
substantially planar "wad-cutter" front surface 342 is recessed
into the cartridge case mouth and driven 150 thousandths of an inch
into the case neck, such that approximately 150 thousandths of the
case neck interior is uncovered by the now inserted back bullet
340, when looking into the cartridge case mouth. Optionally, an
inter-bullet gap defining wadding may be placed upon the distal
surface of back bullet 340. Next a front bullet's proximal flat
base 328 is inserted into the cartridge case mouth and the front
bullet is driven down and preferably seated into abutment with
either the inter-bullet gap defining wadding or with the back
bullet's substantially planar "wad-cutter" front surface 342 so
that the front bullet's proximal flat base 328 is received against
the rear bullet's substantially planar "wad-cutter" front surface
342 when the front bullet 320 is recessed into the cartridge case
mouth and driven 150 thousandths of an inch into the case neck.
Once the duplex cartridge 300 is assembled, the case neck 158
supports the rear of the front bullet and the front of the rear
bullet simultaneously. FIGS. 9B, C and D are photographs of an
altered example of duplex cartridge system 300, where the side of
cartridge case 150 has been cut away to reveal the internal
configuration of these components, and these photographs illustrate
that some of the propellant or powder charge 360 surrounds back
bullet 340 (best seen in FIG. 9D).
[0062] Experiments with prototypes of the duplex cartridge system
of the present invention suggest that an alternative configuration
for the back bullet is useful in creating separation between the
front bullet (e.g., 320) and the back bullet (e.g., 440) in the
rifle's barrel (e.g., 14). Surprising test firing results are shown
on the target images of FIGS. 9E-9G, where, in each case, five
rounds of the subsonic duplex cartridge system of the present
invention were fired at a target 50 yards away, aiming particularly
at the targets' 1/2 inch squares with a suppressed, standard rifle
(e.g., 10). In the test target of FIG. 9E, five shots or rounds
were fired and the first shot's impacts are designated as "1", for
the front bullet (a spritzer, e.g., 320) and "A" for the back
bullet (e.g., wadcutter 340, which makes the distinctive circular
holes). The remaining four shots produced front bullet impacts 2-5
and rear bullet impacts B-E, and the composite group defined by all
10 projectile strikes illustrated in FIG. 9E fit within a 3 inch
circle, meaning that at 50 yards (or about 50 meters), all ten
bullet impacts from five shots group within a six Minute of Angle
(MOA) circle, and within 3 MOA of the aim point (i.e., the 1/2 inch
square). The test firings for similar targets at the same range
with the same rifle illustrated in FIGS. 9F and 9G are similar,
indicating repeatable, reliable ballistic performance.
[0063] Another embodiment of the projectile assembly 400 and method
are illustrated in FIGS. 10A, 10B, 10C, 10D and 10E. A back bullet
440 initially resembling cylindrical projectile 340 has been swaged
or modified to have a substantially squared cross section at the
front or distal wadcutter end 442 (shown in FIGS. 10B, 10D and
10E). The distal swaged end 442 of back bullet 440 creates four
substantially planar angled sidewall surface segments 460, 462,
464, 466 which taper inwardly toward central axis 450A at a taper
angle 470 of 4-8 degrees, terminating distally at distal surface
442 and those angled sidewall surface segments define four "gas
bypass" features at the distal end of back bullet 440, as described
below, The four planar surfaces are swaged into the bullet's
sidewall and each tapers from a transition point 472, where the
sidewall of back bullet 440 is substantially cylindrical from the
four radially arrayed transition points to the proximal end or base
446. The axial length of bullet 440 from transition point 472 to
the distal squared wadcutter end 442 is 0.3 to 0.6 inches for a
bullet 440 having an overall axial length of 1.3 inches.
[0064] Referring specifically to FIGS. 10A-C, duplex projectile
cartridge 400 includes a longitudinally, axially aligned two bullet
assembly comprising front bullet 320 and a back bullet 440 which
also preferably have a combined axial length of 2.260 inches as
carried in a cartridge case 150. Front bullet 320 and back bullet
440 are coaxially aligned with one another and with the case's
central axis 150A and are held in case neck 158 by inwardly
squeezing circumferential force (or "neck tension") applied via the
case neck simultaneously bearing upon and supporting front bullet
320 and back bullet 440, as shown in FIG. 10A. In the illustrated
embodiment, rimless case 150 is substantially identical to the case
used for the M118 cartridge illustrated in FIG. 1B, but other
cartridge cases manufactured in conformance with 7.62 NATO
ammunition specifications may be used. As in the prior embodiment,
front bullet 320 is preferably fabricated or machined from one or
more selected metals (e.g., lead, tungsten, copper alloy cladded
lead, copper alloy cladded tungsten or C36000 brass) preferably
providing a projectile weight of 150 grains.
[0065] Back bullet 440 (see FIGS. 10B and 10C) is preferably
configured with a substantially planar distal surface 442 and is
fabricated or machined from one or more selected metals (e.g.,
lead, tungsten, copper alloy cladded lead, copper alloy cladded
tungsten or C36000 brass) to provide a preferred projectile weight
of 200 grains. The diameter or "caliber" of back bullet 440 is
substantially identical to the front bullet body diameter (e.g.,
for the illustrative example, nominally 0.308 inches or 7.62 mm).
The length of back bullet 240 is preferably 1.3 inches from distal
end (at 442) to base surface 446 (or about 4.22 times the caliber
or largest diameter). The body of back bullet 440 lacks the
conventional rounded or tapered ogive or nose and terminates at the
front (or distally) in the square shaped distal front-facing
surface 442 which is transverse to and symmetrically defined around
the bullet's central axis 450A, and that front facing surface 442
is precisely configured to snugly abut and support the proximal
flat base 328 of coaxially aligned front bullet 320. The proximal
or rearward portion of the body of the back bullet preferably has
rear cylindrical sidewall segment terminating proximally in a
substantially planar transverse rear end or base surface 446 which
provides a flat-base configuration for back bullet 440.
[0066] The method of assembling the duplex ammunition 400 of FIG.
10A is illustrated in FIGS. 10D and 10E. Once a standard military
cartridge case 150 has been primed (not shown), a selected
propellant or powder charge 460 (e.g., Hodgdon H4350 or H1000
smokeless powder) is deposited into the case's interior volume
through the cartridge case mouth 154 (see FIG. 10D). Next, proximal
base 446 of back bullet 440 is placed over case mouth 154 and back
bullet 440 is pressed axially and proximally along axis 150A into
the cartridge case mouth so that back bullet 440 is forced into the
cartridge case's mouth so that the back bullet's distal or forward
substantially planar "wad-cutter" front surface 442 is recessed
into the cartridge case mouth 154 and driven 150 thousandths of an
inch into the case neck 158, such that approximately 150
thousandths of the case neck interior is uncovered by the now
inserted back bullet 440, when looking into the cartridge case
mouth, as best seen in FIG. 10E. Next, a front bullet's proximal
flat base 328 is inserted into the cartridge case mouth 154 and
front bullet 320 is driven proximally down and preferably seated
into abutment with the back bullet's substantially planar
"wad-cutter" front surface 442 so that the front bullet's proximal
flat base 328 is received against the rear bullet's substantially
planar "wad-cutter" front surface 442 when the front bullet 320 is
recessed into the cartridge case mouth and driven 150 thousandths
of an inch into the case neck 158. Once the duplex cartridge 400 is
assembled, the case neck 158 supports the rear of the front bullet
and the front of the rear bullet simultaneously, and (as shown in
FIG. 10E) four gas bypass lumens are provided to vent ignition gas
toward the base 328 of front bullet 320.
[0067] FIG. 10E and FIG. 10A show how the tapered planar wall
segments 460, 462, 464, 466 define four symmetrical gas bypass
lumens between the tapered planar distal sidewall surfaces of
bullet 440 and the cylindrical surface of the interior of cartridge
neck 158, and these four symmetrical gas bypass lumens are
configured and located to allow an optimal amount of propellant gas
to bypass rear projectile 440 when the propellant is ignited by the
primer (not shown).
[0068] Referring now to FIG. 10F, when the propellant charge 460
within case 150 ignites, the back bullet 440 is pushed distally and
out of the case mouth 154 but while the back bullet 440 is still
within case 150, the distal squared sidewall ends provide four
momentary lumens or passages (two of which are seen in FIG. 10E)
for the expanding gas from the burning propellant 460 which
pressurizes the space behind the front bullet (e.g., 320) and
drives it distally down barrel 14 to create an inter-bullet gap
"IBG" 480 between the front bullet 320 and the rear bullet 440.
[0069] Gas bypass duplex projectile assembly 400 provides a
surprisingly effective method for creating the inter bullet gap or
bore axis longitudinal separation "IBG" 480 between the first
bullet 320 and second bullet 440 within the bore (e.g., of barrel
14, as seen in FIG. 10F). Upon firing, the cartridge's ignited
powder 460 creates an expanding gas bubble which initially urges
both the front and back bullets distally into the barrel's leade
(not shown), where front bullet 320 engraves itself on the rifling
and begins to accelerate both in its stabilizing rotation about the
bullet's central axis and in its travel distally down the bore
toward the muzzle. Front bullet 320 is pushed by back bullet 440
and by the bypassing gas from the four bypassing lumens. The four
gas bypass lumens or gas-ducting channels are defined in the distal
or forward surface back bullet 440 to allow expanding gas flowing
distally into the barrel (e.g., 14) behind the distally moving
front bullet 320, to pressurize the base 328 of the front bullet
and force it distally down the bore while back bullet 440 is moving
slightly more slowly, thereby creating the inter-bullet gap "IBG"
480 between the distally forced accelerating front bullet 320 and
the distal or front edge 442 of the slower back bullet 440 as both
bullets travel distally down the bore. This inter bullet gap "IBG"
480 defines a captive or trapped volume of expanding gas between
the front and back bullets as both travel distally down the bore
and allows each bullet to accelerate and engage the barrel's
rifling independently of one another. Within the barrel (e.g., 14),
each bullet 320, 440 is also independently spin stabilized by the
rifling (e.g., standard right hand twist, 1 twist in 12 inches, not
shown), so the barrel's rifling twist rate need not be optimized
for a very, very long and heavy (e.g., 350 grains) single bullet
(or abutting front and rear bullets which spin and act as one long
350 gr projectile) and instead a standard (e.g., 1:12) twist rate
stabilizes front bullet 320 separately and independently from rear
bullet 440, as seen in FIG. 10F.
[0070] Turning now to FIGS. 11A-14B, four alternative embodiments
for the duplex projectile system ammunition assembly (500, 600,
700, and 800) are illustrated, where each embodiment provides an
alternative configuration and method for creating an inter-bullet
gap "IBG" 480 or longitudinal separation between the first and
second bullets (as seen in FIG. 10F), in accordance with the
present invention.
[0071] FIGS. 11A, 11B, 11C and 11D illustrate front, rear, and
cross sectional side views of a ducted gas bypass duplex projectile
system ammunition assembly 500, where front bullet 320 is
preferably configured as a spitzer with a flat circular base and
the body of front bullet 320 has a tapered or contoured ogive
terminating distally in a distal solid tip or a front facing cavity
or opening symmetrically defined around the central axis, and the
front facing cavity may be configured to receive a polymer
ballistic tip insert (not shown). The diameter or "caliber" of the
front bullet body is preferably selected from among SAAMI standard
calibers (e.g., nominally 0.308 inches or 7.62 mm) for use in a
selected rifle (e.g., 10). The central portion of the body of front
bullet 320 may optionally include a sidewall segment carrying a
plurality of circumferential grooves of shallow depth and spaced
longitudinally along the bullet sidewall from one another or a
knurled segment (not shown). The proximal or rearward portion 326
of the body of the front bullet preferably has rear cylindrical
sidewall segment terminating proximally in a transverse flat,
circular base 328 which is symmetrically defined around the front
bullet body's central axis, and the substantially planar transverse
rear flat base surface 328 is configured to abut a substantially
planar ported or ducted front surface 542 defined in back bullet
540, although an inter-bullet starter gap may be defined
therebetween or filled with an optional wadding disc (not
shown).
[0072] Back bullet 540 is fabricated or machined from a selected
metal or is configured with a cladding metal jacket over a lead
core. The diameter or "caliber" of the back bullet is substantially
identical to the front bullet body diameter (e.g., for the
illustrative example, nominally 0.308 inches or 7.62 mm). The body
of back bullet 540 lacks a conventional rounded or tapered nose and
terminates at the front (or distally) in a full-diameter
substantially planar "wad-cutter" front surface 542 symmetrically
defined around the bullet's central axis, and that "wad-cutter"
front surface 542 is preferably configured to snugly abut and
support the flat base 328 of the coaxially aligned front bullet
320, although an inter-bullet gap (as in FIG. 9C) may be defined
therebetween or filled with an optional wadding disc (not shown).
The central portion of the body of the back bullet 540 preferably
includes a sidewall segment carrying a plurality of transverse
apertures, lumens or ports 544 of small inside diameter (e.g., 0.05
inch ID) which are also in fluid communication with a longitudinal
or axial lumen or longitudinal axial duct 545 which permits
expanding gas from ignited propellant to pass distally through the
solid interior of back bullet 540 to pressurize the space behind
front bullet 320, when fired. The proximal or rearward portion of
the body of the back bullet preferably has rear cylindrical
sidewall segment terminating proximally in a tapered sidewall with
a reduced diameter substantially planar transverse rear end to
provide a boat-tail back bullet configuration.
[0073] The method of assembling the duplex ammunition 500 of FIGS.
11A-D is similar to that described above and illustrated in FIGS.
10D and 10E. Once a standard military cartridge case 150 has been
primed (not shown), a selected propellant or powder charge 460
(e.g., Hodgdon H4350 or H1000 smokeless powder) is deposited into
the case's interior volume through the cartridge case mouth. Next,
proximal base of back bullet 540 is placed over case mouth 154 and
back bullet 540 is pressed axially and proximally along axis 150A
into the cartridge case mouth so that back bullet 540 is forced
into the cartridge case's mouth and the back bullet's distal or
forward substantially planar "wad-cutter" front surface 542 is
recessed into the cartridge case mouth 154 and driven 150
thousandths of an inch into the case neck 158 such that
approximately 150 thousandths of the case neck interior is
uncovered by the now inserted back bullet 540. Next, a front
bullet's proximal flat base 328 is inserted into the cartridge case
mouth 154 and front bullet 320 is driven proximally down and
preferably seated into abutment with the back bullet's
substantially planar "wad-cutter" front surface so that the front
bullet's proximal flat base 328 is received against the rear
bullet's substantially planar "wad-cutter" front surface when the
front bullet 320 is recessed into the cartridge case mouth and
driven 150 thousandths of an inch into the case neck 158. Once the
duplex cartridge 500 is assembled, the case neck 158 supports the
rear of the front bullet and the front of the rear bullet
simultaneously, and (as shown in FIG. 11B) the gas bypass lumens
544, 545 are provided to vent ignition gas toward the base 328 of
front bullet 320.
[0074] FIGS. 11B and 11D show how the gas bypass lumens within back
bullet 540 are configured and located to allow an optimal amount of
propellant gas to bypass rear projectile 540 when the propellant is
ignited by the primer (not shown). When the primer ignites the
propellant charge 460, the back bullet 540 is pushed distally and
out of the case mouth 154 but while the back bullet is still within
case 150, the bypass lumens 544, 545 provide momentary passages for
the expanding gas from the burning powder 460 which pressurizes the
space behind the front bullet (e.g., 320) and drives it down the
barrel (e.g., 14) to create an inter-bullet gap (e.g., "IBG" 480)
between the front bullet 320 and the rear bullet 540.
[0075] Gas bypass duplex projectile assembly 500 also provides a
surprisingly effective method for creating separation (e.g., "IBG"
480) between the first bullet 320 and second bullet 540 within the
bore (e.g., of rifle 10). Upon firing, the cartridge's ignited
powder 460 creates an expanding gas bubble which initially urges
both the front and back bullets distally into the barrel's leade
(not shown), where front bullet 320 engraves itself on the rifling
and begins to accelerate both in its stabilizing rotation about the
bullet's central axis and in its travel distally down the bore
toward the muzzle. Front bullet 320 is pushed by back bullet 540
and by bypassing expanding gas from lumen 545. The gas bypass
lumens or gas-ducting channels 544, 545 are in fluid communication
with the distal or forward surface of back bullet 540 to direct
expanding gas flowing distally into the barrel behind the distally
moving front bullet 320 to pressurize the base 328 of the front
bullet and force it distally down the bore while back bullet 540 is
moving slightly more slowly, thereby creating the inter-bullet gap
(e.g., "IBG" 480) between the distally forced accelerating front
bullet 320 and the distal or front edge 542 of the slower back
bullet as both bullets travel distally down the bore. This inter
bullet gap (e.g., "IBG" 480) defines a captive or trapped volume of
expanding gas between the front and back bullets as both travel
distally down the bore and allows each bullet to accelerate and
engage the barrel's rifling independently. Within the barrel (e.g.,
of rifle 10), each bullet 320, 540 is also independently spin
stabilized by the rifling, so the rifling twist rate need not be
optimized for a very, very long and heavy (e.g., 350 grains) single
bullet (or abutting bullets which spin and act as one) and instead
a standard twist rate stabilizes front bullet 320 separately and
independently from rear bullet 540.
[0076] FIGS. 12A, 12B, 12C, 12D, 12E, 12F and 12G illustrate
another alternative embodiment for the duplex projectile system
ammunition assembly 600 where front bullet 320 is preferably
configured as a spitzer with a flat circular base and the body of
front bullet 320 has a tapered or contoured ogive terminating
distally in a distal solid tip or a front facing cavity or opening
symmetrically defined around the central axis, and the front facing
cavity may be configured to receive a polymer ballistic tip insert
(not shown). The diameter or "caliber" of the front bullet body is
preferably selected from among SAAMI standard calibers (e.g.,
nominally 0.308 inches or 7.62 mm) for use in a selected rifle
(e.g., 10). The central portion of the body of front bullet 320 may
optionally include a sidewall segment carrying a plurality of
circumferential grooves of shallow depth and spaced longitudinally
along the bullet sidewall from one another or a knurled segment
(not shown). Alternatively, a soft-point front bullet such as the
Sierra Game King.TM. (e.g., 320SP) may be substituted. The proximal
or rearward portion 326 of the body of the front bullet preferably
has rear cylindrical sidewall segment terminating proximally in a
transverse flat, circular base 328 which is symmetrically defined
around the front bullet body's central axis, and the substantially
planar transverse rear flat base surface 328 is configured to abut
a substantially planar transverse front surface or wide meplat 642
of the tapered-ogive back bullet 640, although an inter-bullet
starter gap may be defined therebetween or filled with an optional
wadding disc (not shown).
[0077] Tapered Ogive back bullet 640 is fabricated or machined from
a selected metal or is configured with a cladding metal jacket over
a lead core. The body diameter or "caliber" of the back bullet is
substantially identical to the front bullet body diameter (e.g.,
for the illustrative example, nominally 0.308 inches or 7.62 mm).
The body of back bullet 640 lacks a conventional pointed nose and
terminates at the front (or distally) in a reduced-diameter
substantially planar meplat front surface defining a circular
surface symmetrically defined around the bullet's central axis, and
that meplat front surface 642 is preferably or forced to snugly
abut and support the flat base 328 of the coaxially aligned front
bullet 320, although an inter-bullet gap (as seen in FIG. 9C) may
be defined therebetween or filled with an optional wadding disc
(not shown). The distal tapered ogive portion of the body of the
back bullet 640 which terminated distally in meplat 642 is in fluid
communication with the longitudinal lumen in the cartridge neck 158
and permits expanding gas to flow or pass distally through around
back bullet 640 to pressurize the space behind front bullet 320,
when fired. The proximal or rearward portion of the body of back
bullet 640 preferably has rear cylindrical sidewall segment
terminating proximally in a tapered sidewall with a reduced
diameter substantially planar transverse rear end to provide a
boat-tail back bullet configuration.
[0078] The method of assembling the duplex ammunition 600 as
illustrated in FIGS. 12A-12G is similar to that described above and
illustrated in FIGS. 10D and 10E. Once a standard military
cartridge case 150 has been primed (not shown), a selected
propellant or powder charge 460 (e.g., Hodgdon H4350 or H1000
smokeless powder) is deposited into the case's interior volume
through the cartridge case mouth 154 (see FIG. 12G). Next, proximal
"boat tail" base of back bullet 640 is placed over case mouth 154
and back bullet 640 is pressed axially and proximally along axis
150A into the cartridge case mouth so that back bullet 640 is
forced into the cartridge case's mouth and the back bullet's distal
or forward front surface (see meplat 642 in FIG. 12G) is recessed
into the cartridge case mouth 154 and driven 150 thousandths of an
inch into the case neck 158, such that approximately 150
thousandths of the case neck interior is uncovered by the now
inserted back bullet 640, and the back bullet 640 is supported in
this orientation partly by the powder charge within the case. Next,
a front bullet's proximal flat base 328 is inserted into the
cartridge case mouth 154 and front bullet 320 is driven proximally
down farther than 150 thousandths (e.g., 280 thousandths) to force
base into engagement against the back bullet's meplat 642.
Referring now to the photographs in FIGS. 12E-12G, Back or rear
bullet 642 may be fabricated from a Sierra Match King .308 OTM
projectile (normally 1.489 inches long) which has had the open tip
cut or milled off to leave a substantially cylindrical bullet body
with a slight tapered ogive in the distal sidewall and an overall
length of 1.050 inches. That nearly cylindrical bullet body is then
inserted distal end first into a hemispherical rounding die to
create a distally bulging dome shape from the exposed lead core at
the distal end 642B, as shown in FIG. 12E. The distal meplat
surface 642 (best seen in FIG. 12G) may be then applied by a die or
by forcing the flat base 328 of front bullet 320 against the softer
lead core of back bullet to create transverse circular meplat 642,
which preferably has a planar diameter of at least 0.150 inches (or
about half the diameter or caliber of the body of back bullet
640.
[0079] During assembly of duplex cartridge 600, the front bullet's
proximal flat base 328 drives against and is received against the
rear bullet's substantially planar "wad-cutter" like meplat front
surface 642 when the front bullet 320 is recessed into the
cartridge case mouth and driven 280 thousandths of an inch into the
case neck 158. Once the duplex cartridge 600 is assembled, the case
neck 158 supports the rear of front bullet 320 but the front of
rear bullet 640 is driven into the case enough to create an annular
gas bypass lumen around the distal end 642 of front bullet 640. As
shown in FIGS. 12B and 12D (and in the photograph of cut-away
casing 150V revealing the cartridge's interior of FIG. 12F) a gas
bypass annular lumen is provided at the reduced diameter ogive in
the distal end 642 of back bullet 640 to vent ignition gas toward
the base 328 of front bullet 320, and the transverse gap width of
that gas bypass lumen is between five thousandths and ten
thousandths of an inch. Thus, the gas bypass lumen area for the
exemplary cartridge 600 of FIGS. 12A-12G is defined by an annulus
having an inside diameter of 0.308 inches and an outside diameter
of 0.313 and 0.318 inches.
[0080] FIGS. 12B and 12D show how the annular gas bypass lumen
around the distal end of back bullet 640 configured and located to
allow an optimal amount of propellant gas to bypass rear projectile
640 when the propellant is ignited by the primer (not shown). When
the primer ignites the propellant charge 460, the back bullet 640
is pushed distally and out of the case mouth 154 but while the back
bullet is still within case 150, the annular bypass lumen provides
momentary passages for the expanding gas from the burning powder
460 which pressurizes the space behind the front bullet (e.g., 320)
and drives it down the barrel (e.g., 14) to create an inter-bullet
gap (e.g., "IBG" 480) between the front bullet 320 and the rear
bullet 640.
[0081] Gas bypass duplex projectile assembly 600 also provides a
surprisingly effective method for creating separation (e.g., "IBG"
480) between the first bullet 320 and second bullet 640 within the
bore (e.g., of rifle 10). Upon firing, the cartridge's ignited
powder 460 creates an expanding gas bubble which initially urges
both the front and back bullets distally into the barrel's leade
(not shown), where front bullet 320 engraves itself on the rifling
and begins to accelerate both in its stabilizing rotation about the
bullet's central axis and in its travel distally down the bore
toward the muzzle. Front bullet 320 is pushed by back bullet 640
and by the expanding gas from the propellant. The annular gas
bypass lumen or gas-ducting channel defined around the forward
surface 642 of back bullet 640 directs expanding gas to flow
distally into the barrel behind the distally moving front bullet
320 to pressurize the base 328 of the front bullet and force it
distally down the bore while back bullet 640 is moving slightly
more slowly, thereby creating the desired inter-bullet gap (e.g.,
"IBG" 480) between the distally forced accelerating front bullet
320 and the distal or front edge 642 of the slower back bullet as
both bullets travel distally down the bore. This inter bullet gap
(e.g., "IBG" 480) defines a captive or trapped volume of expanding
gas between the front and back bullets as both travel distally down
the bore and allows each bullet to accelerate and engage the
barrel's rifling independently. Within the barrel (e.g., 14), each
bullet 320, 640 is also independently spin stabilized by the
rifling, so the rifling twist rate need not be optimized for a
very, very long and heavy (e.g., 350 grains) single bullet (or
abutting bullets which spin and act as one) and instead a standard
twist rate stabilizes front bullet 320 separately and independently
from rear bullet 640.
[0082] FIGS. 13A, 13B, 13C and 13D illustrate yet another gas
bypass embodiment for the duplex projectile system ammunition
assembly 700, where front bullet 320 is preferably configured as a
spitzer with a flat circular base and the body of front bullet 320
has a tapered or contoured ogive terminating distally in a distal
solid tip or a front facing cavity or opening symmetrically defined
around the central axis, and the front facing cavity may be
configured to receive a polymer ballistic tip insert (not shown).
The diameter or "caliber" of the front bullet body is preferably
selected from among SAAMI standard calibers (e.g., nominally 0.308
inches or 7.62 mm) for use in a selected rifle (e.g., 10). The
central portion of the body of front bullet 320 may optionally
include a sidewall segment carrying a plurality of circumferential
grooves of shallow depth and spaced longitudinally along the bullet
sidewall from one another or a knurled segment (not shown). The
proximal or rearward portion of the body of the front bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a transverse flat, circular base 328 which is
symmetrically defined around the front bullet body's central axis,
and the substantially planar transverse rear flat base surface 328
is configured to abut a substantially planar ported front surface
of the back bullet 740, although an inter-bullet starter gap may be
defined therebetween or filled with an optional wadding disc (not
shown).
[0083] Back bullet 740 is fabricated or machined from a selected
metal or is configured with a cladding metal jacket over a lead
core. The diameter or "caliber" of the back bullet is substantially
identical to the front bullet body diameter (e.g., for the
illustrative example, nominally 0.308 inches or 7.62 mm). The body
of back bullet 740 lacks a conventional rounded or tapered nose and
terminates at the front (or distally) in a full-diameter
substantially planar "wad-cutter" front surface symmetrically
defined around the bullet's central axis, and that "wad-cutter"
front surface is preferably configured to snugly abut and support
the flat base of the coaxially aligned front bullet 320, although
an inter-bullet gap (as seen in FIG. 9C) may be defined
therebetween or filled with an optional wadding disc (not shown).
The body of the back bullet 740 preferably includes a sidewall
segment carrying a plurality of radially spaced longitudinal
grooves or vias 744 which define longitudinal gas bypass ports or
lumens in fluid communication with the space behind the front
bullet 320. Those longitudinal lumen-defining grooves 744 direct
expanding gas to pass distally through around and through back
bullet 740 to pressurize the space behind front bullet 320, when
fired. The proximal or rearward portion of the body of the back
bullet preferably has rear cylindrical sidewall segment terminating
proximally in a tapered sidewall with a reduced diameter
substantially planar transverse rear end to provide a boat-tail
back bullet configuration.
[0084] The method of assembling the duplex ammunition 700 of FIGS.
13A-D is similar to that described above and illustrated in FIGS.
10D and 10E. Once a standard military cartridge case 150 has been
primed (not shown), a selected propellant or powder charge 460
(e.g., Hodgdon H4350 smokeless powder) is deposited into the case's
interior volume through the cartridge case mouth 154. Next,
proximal base of back bullet 740 is placed over case mouth 154 and
back bullet 540 is pressed axially and proximally along axis 150A
into the cartridge case mouth so that back bullet 740 is forced
into the cartridge case's mouth and the back bullet's distal or
forward substantially planar "wad-cutter" front surface is recessed
into the cartridge case mouth 154 and driven 150 thousandths of an
inch into the case neck 158, such that approximately 150
thousandths of the case neck interior is uncovered by the now
inserted back bullet 740. Next, a front bullet's proximal flat base
328 is inserted into the cartridge case mouth 154 and front bullet
320 is driven proximally down and preferably seated into abutment
with the back bullet's substantially planar "wad-cutter" front
surface so that the front bullet's proximal flat base 328 is
received against the rear bullet's substantially planar
"wad-cutter" front surface when the front bullet 320 is recessed
into the cartridge case mouth and driven 150 thousandths of an inch
into the case neck 158. Once the duplex cartridge 700 is assembled,
the case neck 158 supports the rear of the front bullet and the
front of the rear bullet simultaneously, and (as shown in FIG. 13B)
the gas bypass grooves or lumens 744 are provided to vent ignition
gas toward the base 328 of front bullet 320.
[0085] FIGS. 13B and 13D show how the gas bypass lumens within back
bullet 740 are configured and located to allow an optimal amount of
propellant gas to bypass rear projectile 740 when the propellant is
ignited by the primer (not shown). When the primer ignites the
propellant charge 460, the back bullet 740 is pushed distally and
out of the case mouth 154 but while the back bullet is still within
case 150, the bypass grooves or lumens 744 provide momentary
passages which direct or aim the expanding gas from the burning
powder 460 to pressurize the space behind the front bullet (e.g.,
320) and drives it down the barrel of rifle 10 to create an
inter-bullet gap between the front bullet 320 and the rear bullet
740.
[0086] Gas bypass duplex projectile assembly 700 also provides a
surprisingly effective method for creating separation (e.g., "IBG"
480) between the first bullet 320 and second bullet 540 within the
bore (e.g., of rifle 10). Upon firing, the cartridge's ignited
powder 460 creates an expanding gas bubble which initially urges
both the front and back bullets distally into the barrel's leade
(not shown), where front bullet 320 engraves itself on the rifling
and begins to accelerate both in its stabilizing rotation about the
bullet's central axis and in its travel distally down the bore
toward the muzzle. Front bullet 320 is pushed by back bullet 740
and by expanding gas from grooves 744. The gas bypass lumens or
gas-ducting channels 744 are defined in the distal or forward
surface of back bullet 740 to allow expanding gas flowing distally
into the barrel behind the distally moving front bullet 320, to
pressurize the base 328 of the front bullet and force it distally
down the bore while back bullet 740 is moving slightly more slowly,
thereby creating an inter-bullet gap between the distally forced
accelerating front bullet 320 and the distal or front edge of the
slower back bullet 740 as both bullets travel distally down the
bore. This inter bullet gap defines a captive or trapped volume of
expanding gas between the front and back bullets as both travel
distally down the bore and allows each bullet to accelerate and
engage the barrel's rifling independently. Within the barrel (e.g.,
of rifle 10), each bullet 320, 740 is also independently spin
stabilized by the rifling, so the rifling twist rate need not be
optimized for a very, very long and heavy (e.g., 350 grains) single
bullet (or abutting bullets which spin and act as one) and instead
a standard twist rate stabilizes front bullet 320 separately and
independently from rear bullet 740.
[0087] Finally, FIGS. 14A and 14B illustrate another alternative
embodiment for the duplex projectile system ammunition assembly
800, where front bullet 320 is preferably configured as a spitzer
with a flat circular base and the body of front bullet 320 has a
tapered or contoured ogive terminating distally in a distal solid
tip or a front facing cavity or opening symmetrically defined
around the central axis, and the front facing cavity may be
configured to receive a polymer ballistic tip insert (not shown).
The diameter or "caliber" of the front bullet body is preferably
selected from among SAAMI standard calibers (e.g., nominally 0.308
inches or 7.62 mm) for use in a selected rifle (e.g., 10). The
central portion of the body of front bullet 320 may optionally
include a sidewall segment carrying a plurality of circumferential
grooves of shallow depth and spaced longitudinally along the bullet
sidewall from one another or a knurled segment (not shown). The
proximal or rearward portion 326 of the body of the front bullet
preferably has rear cylindrical sidewall segment terminating
proximally in a transverse flat, circular base 328 which is
symmetrically defined around the front bullet body's central axis,
and the substantially planar transverse rear flat base surface 328
is configured to abut a substantially planar ported front surface
842 of back bullet 840, although an inter-bullet starter gap may be
defined therebetween or filled with an optional wadding disc (not
shown).
[0088] Back bullet 840 is fabricated or machined from a selected
metal or is configured with a cladding metal jacket over a lead
core. The diameter or "caliber" of the back bullet is substantially
identical to the front bullet body diameter (e.g., for the
illustrative example, nominally 0.308 inches or 7.62 mm). The body
of back bullet 840 lacks a conventional rounded or pointed nose and
tapers slightly to terminate at the front (or distally) in a nearly
full-diameter substantially planar "wad-cutter" front surface
symmetrically defined around the bullet's central axis, and that
"wad-cutter" front surface 842 is preferably configured to snugly
abut and support the flat base of the coaxially aligned front
bullet 320, although an inter-bullet gap may be defined
therebetween or filled with an optional wadding disc (not shown).
The body of the back bullet 840 preferably includes a sidewall
segment carrying a plurality of radially spaced longitudinal
grooves or vias 844 which define longitudinal lumens in fluid
communication with the space behind the front bullet 320 and the
propellant. Those longitudinal lumen-defining grooves 844 direct
expanding gas to pass distally through around and through back
bullet 840 to pressurize the space behind front bullet 320, when
fired. The proximal or rearward portion of the body of the back
bullet preferably has rear cylindrical sidewall segment terminating
proximally in a tapered sidewall with a reduced diameter
substantially planar transverse rear end to provide a boat-tail
back bullet configuration.
[0089] For the gas-bypass embodiments illustrated in FIGS. 11A-14B,
the duplex projectile system ammunition assembly (e.g., 500, 600,
700 or 800) a taper crimp is preferably applied to secure the case
neck's retention of front bullet 320. Preferably, a boron nitride
coating is applied to at least front bullet 320, preferably with a
coating thickness of approximately one micron, which enhances
static friction between the sidewall of front bullet 320 and the
interior surface of the case neck 158. At present, an alternative
preferred propellant charge (for 160, 260, 360 and 460) is about 23
grains of H-1000 powder (which may be seen by those of skill in the
art to be a powder selection providing a slower than expected burn
rate.)
[0090] The duplex projectile system ammunition assembly (e.g., 500,
600, 700 or 800) of the present invention has been configured to
provide a surprising advancement in extreme impact subsonic
ammunition, wherein the subsonic embodiment of the ammunition
carries front and back projectiles having a combined total weight
of 350 grains or more, and when fired, the front and back bullets
impact in very close proximity to each other, delivering dramatic
results on a target. Each duplex cartridge (e.g., in 308 Win or
7.62 NATO) will function and fully stabilize in a .308 Win.-based
semi-auto platform rifle (e.g., 10) with no modifications to the
rifle gas system, so subsonic duplex loads (e.g., 500, 600, 700 or
800) and supersonic loads may be fired from the same magazine with
no other special considerations. For the embodiments illustrated in
FIGS. 11A-14B, the duplex projectile system ammunition assembly
(e.g., 500, 600, 700 or 800) of the present invention provides
projectiles optimized to be compatible with 1-12 and faster twist
rate barrels (e.g., 14).
[0091] The front bullet (e.g., 320) is designed to shoot smaller
groups and is assigned the designation of the ammunition's "zero."
The trailing, second or back bullet (e.g., 540) is constructed as a
wadcutter/full-diameter/open-tip. When the shooter or user observes
groups on the target, it is easy to distinguish each bullet's
impact (as described above and illustrated in FIGS. 9E-9G). This
ammunition is engineered and intended for use at relatively short
ranges (e.g., up to 100 yards), but can be used to engage targets
at 200 yds. For example, in a hunting application, the impact
distance between the front and the rear bullet is engineered to
produce a dual-hit head shot on a pig size target with "double-tap"
efficiency from a single fired .308 round. Testing has shown that a
full 50-round box of the duplex ammo of the present invention
(having 100 projectiles) will produce a composite group of less
than 3 inches at 50 yards.
[0092] The kinetic energy delivered to the target when using the
ammunition configuration of the present invention is superior. For
example, comparing the cartridges described above (e.g., 500, 600,
700 or 800) to "300 Blackout" ammunition, the BLACKOUT subsonic
ammunition fires a 200-grain bullet at 1075 fps to provide 471
ft-lbs of muzzle energy. BLACKOUT supersonic ammunition has a
110-grain bullet at 2300 fps which provides 823 ft-lbs of muzzle
energy. The ammunition of the present invention (subsonic)
provides: 350 grain total bullet mass (2 projectiles) at 1075
fps=816 ft-lbs of muzzle energy. So the subsonic 308 load of the
present invention provides superior energy on target (816 ft-lbs)
compared to the subsonic 300 Blackout load, and substantially
equals the supersonic Blackout load's energy at 100 yards.
[0093] In the illustrated embodiments, the duplex projectile system
of the present invention (e.g., 100, 200, 300, 500, 600, 700, or
800) is optimized to provide subsonic ammunition which is adapted
for use in a standard rifle (e.g., 10) equipped with a suppressor
(e.g., 12) or silencer. When a gas operated rifle (e.g. 10) is
equipped with a suppressor (e.g., 12). The duplex projectile system
of the present invention (e.g., 100, 200, 300, 500, 600, 700, or
800) creates significantly more gas port pressure than standard
subsonic ammo, thus allowing standard rifles (e.g., 10) to function
without requiring any gas system adjustment or requiring a
substitution of louder supersonic ammunition. This benefit is
important because the first and second bullets of the duplex system
(e.g., 100, 200, 300, 400, 500, 600, 700, or 800) weigh more than
any single bullet ever manufactured for use in a standard rifle 10.
The firing of the duplex (front and rear) bullets require a higher
gas pressure to reach the selected subsonic velocity desired (e.g.
1050 fps). This higher gas pressure makes it possible for an
unaltered standard rifle 10 to function without adjusting the gas
system. No other subsonic or volley ammunition can provide reliable
gas system operation and consistent shot-to-shot subsonic accuracy
in standard rifles.
[0094] Significantly, this level of performance (as illustrated in
FIGS. 9E-9G is achieved in part because the barrels in standard
rifles provide surprising stability for the first and second
projectiles of the duplex projectile system (e.g., 100, 200, 300,
400, 500, 600, 700, or 800). A standard rifle (e.g., 10) typically
has a rifling twist rate of between one in ten inches to one in
twelve inches and is designed to stabilize a single projectile of
147 grains to 175 grains travelling at the standard supersonic
velocity (e.g., 2650 fps-2800 fps). In the present invention, the
front and back bullets are stabilized in a standard twist-rate
rifle at the selected subsonic velocity (e.g. 1050 fps). The
applicants have discovered how to provide the enhanced terminal
ballistic benefits of firing a single long and heavy bullet at
subsonic velocities, but without requiring a different barrel; a
single long bullet that weighed the same amount as the duplex
system's front and back bullets (e.g., 350 Gr.) would be too long
to be stabilized in a standard twist-rate rifle (e.g., 10).
[0095] In the prototypes developed and tested so far, the preferred
velocity (e.g. 1050 fps) for the bullets in the duplex projectile
system (e.g., 100, 200, 300, 400, 500, 600, 700, or 800) was
generated with a propellant charge (e.g., 360) comprising 20 grains
of H4350 powder when used with a Large Rifle Magnum primer. The
front and back bullets of the duplex system (e.g., 100, 200, 300,
400, 500, 600, 700, or 800) can be manufactured precisely and
economically by standard methods including casting, swaging or
pressing metal alloy components into the desired
configurations.
[0096] Having described preferred embodiments of a new and improved
method, it is believed that other modifications, variations and
changes will be suggested to those skilled in the art in view of
the teachings set forth herein. It is therefore to be understood
that all such variations, modifications and changes are believed to
fall within the scope of the present invention as defined by the
following claims.
* * * * *