U.S. patent application number 10/341224 was filed with the patent office on 2003-07-17 for subsonic and reduced velocity ammunition cartridges.
Invention is credited to MacKerell, Brad, Payne, Ryan.
Application Number | 20030131751 10/341224 |
Document ID | / |
Family ID | 23364542 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030131751 |
Kind Code |
A1 |
MacKerell, Brad ; et
al. |
July 17, 2003 |
Subsonic and reduced velocity ammunition cartridges
Abstract
Subsonic and reduced velocity rifle ammunition cartridges are
disclosed. The ammunition cartridges can be fired through a
standard rifle with a common twist rate at subsonic and reduced
velocities. The subsonic ammunition uses propellant that is not
typically used with the selected rifle cartridge. Cycling subsonic
ammunition cycles the firing and loading mechanisms of fully
automatic and semiautomatic weapons. Cycling subsonic ammunition
cartridges contain slow burning propellant, such as cannon powder,
and a heavy projectile with a long bearing surface. Non-cycling
subsonic ammunition uses moderately fast burning pistol propellant.
The projectiles are carefully selected to be stable at subsonic or
reduced velocities and at the standard rifle twist rate for given
cartridge caliber.
Inventors: |
MacKerell, Brad; (Draper,
UT) ; Payne, Ryan; (Pleasant Grove, UT) |
Correspondence
Address: |
MADSON & METCALF
GATEWAY TOWER WEST
SUITE 900
15 WEST SOUTH TEMPLE
SALT LAKE CITY
UT
84101
|
Family ID: |
23364542 |
Appl. No.: |
10/341224 |
Filed: |
January 13, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60347629 |
Jan 11, 2002 |
|
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Current U.S.
Class: |
102/447 |
Current CPC
Class: |
F42B 5/02 20130101; F42B
5/16 20130101; F42B 5/025 20130101; F42B 8/00 20130101 |
Class at
Publication: |
102/447 |
International
Class: |
F42B 005/16; F42B
008/00 |
Claims
1. A subsonic or reduced velocity ammunition cartridge comprising:
a standard rifle cartridge casing having a base end and an open
end, sized to be used with a standard rifle having a standard rifle
twist rate, said cartridge casing having an internal volume; a
primer inserted in the base end of the casing; a quantity of
propellant disposed within the casing, wherein the propellant is
not a standard rifle propellant; and a projectile sized to fit
within the open end of the casing and which is stable at subsonic
velocity and at the rifle twist rate.
2. The cartridge of claim 1, wherein the projectile is selected to
have a center of mass that is approximately equal to the center of
length.
3. The cartridge of claim 1, wherein the propellant is a moderately
fast burn rate pistol propellant.
4. The cartridge of claim 3, wherein the quantity of propellant is
in the range from about 15 to 20%, by weight, of the propellant
used in a standard supersonic rifle cartridge using the cartridge
casing.
5. The cartridge of claim 1, wherein the propellant is spherical
powder.
6. The cartridge of claim 1, wherein the cartridge casing is
colored to identify the cartridge as a subsonic ammunition
cartridge.
7. The cartridge of claim 6, wherein the cartridge casing is
colored black.
8. The cartridge of claim 1, wherein the projectile, when fired
from the rifle, travels at subsonic or reduced velocity that
stabilizes and maintains sufficient energy to be lethal and
penetrate modern body armor.
9. The cartridge of claim 1, wherein the cartridge may be used with
a rifle equipped with a sound suppressor.
10. The cartridge of claim 1, wherein the projectile, when fired
from the rifle, travels at subsonic or reduced velocity that
stabilizes and follows a predictable trajectory.
11. The cartridge of claim 1, wherein the projectile, when fired
from the rifle, travels at subsonic or reduced velocity that
stabilizes and follows a predictable trajectory at a range up to
about 200-800 yards depending on caliber.
12. The cartridge of claim 1, wherein the projectile, when fired
from the rifle, travels at subsonic or reduced velocity that
stabilizes and achieves Minute of Angle at 100 yards.
13. The cartridge of claim 1, wherein the rifle is an automatic or
semiautomatic rifle having a cycling firing mechanism, wherein the
projectile travels as subsonic or reduced velocity when fired from
the rifle, and wherein the cartridge produces sufficient pressure
to cycle the firing mechanism.
14. The cartridge of claim 13, wherein the projectile is heavier
than a comparable projectile designed for supersonic flight for use
with the rifle cartridge casing.
15. The cartridge of claim 13, wherein the projectile has a longer
bearing surface than a comparable projectile designed for
supersonic flight and use with the rifle cartridge casing.
16. The cartridge of claim 13, wherein the propellant is cannon
propellant.
17. The cartridge of claim 1, wherein the rifle cartridge is a .223
caliber cartridge containing from 3.5 to 4.5 grains of pistol
propellant and a projectile weighing from 50 to 60 grains.
18. The cartridge of claim 1, wherein the rifle cartridge is a .308
caliber cartridge containing from 6 to 9 grains of pistol
propellant and a projectile weighing from 150 to 220 grains.
19. The cartridge of claim 1, wherein the rifle cartridge is a .50
BMG cartridge containing from 20 to 60 grains of pistol propellant
and a projectile weighing from 525 to 900 grains.
20. The cartridge of claim 1, wherein the rifle cartridge is a .300
Winchester Magnum cartridge containing from 8 to 16 grains of
pistol propellant and a projectile weighing from 150 to 230
grains.
21. The cartridge of claim 1, wherein the rifle cartridge is a
7.62.times.39mm cartridge containing from 7.5 to 8.5 grains of
pistol propellant and a projectile weighing from 170 to 190
grains.
22. The cartridge of claim 13, wherein the rifle cartridge is a
.223 caliber cartridge containing from 18 to 25 grains of cannon
propellant and a projectile weighing from 90 to 125 grains.
23. The cartridge of claim 22, wherein the projectile has a bearing
surface ranging from 0.4 to 1.1 inches.
24. The cartridge of claim 22, wherein the projectile has a bearing
surface ranging from 0.8 to 0.9 inches.
25. A method of making a subsonic or reduced velocity ammunition
cartridge comprising: obtaining a standard rifle cartridge casing
having a base end and an open end, sized to be used with a standard
rifle having a standard rifle twist rate, said cartridge casing
having an internal volume, wherein a primer is inserted in the base
end of the casing; selecting a projectile sized to fit within the
open end of the casing which is stable at subsonic or reduced
velocity and at the standard rifle twist rate; selecting a
moderately fast burning pistol propellant; disposing a quantity of
the propellant within the casing, wherein the quantity of
propellant is selected to leave substantial void space within the
casing internal volume and to generate sufficient pressure upon
ignition to expel the projectile at subsonic or reduced velocity;
and disposing the projectile within the open end of the casing.
26. A method of making a subsonic or reduced velocity ammunition
cartridge that can cycle the firing and loading action of an
automatic or semiautomatic rifle, comprising: obtaining a standard
rifle cartridge casing having a base end and an open end, sized to
be used with a standard automatic or semiautomatic rifle having a
standard rifle twist rate, said cartridge casing having an internal
volume, wherein a primer is inserted in the base end of the casing;
selecting a projectile sized to fit within the open end of the
casing which is stable at subsonic or reduced velocity and at the
standard rifle twist rate, wherein the projectile is heavier and
has a longer bearing surface than a comparable projectile designed
for supersonic flight for use with the rifle cartridge casing;
selecting a slow burning cannon propellant; disposing a quantity of
the propellant within the casing, wherein the quantity of
propellant is selected to generate sufficient pressure upon
ignition to expel the projectile at subsonic or reduced velocity
and to cycle the firing and loading action; and disposing the
projectile within the open end of the casing.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/347,629, filed Jan. 11, 2002.
FIELD OF THE INVENTION
[0002] The invention is directed to subsonic and reduced velocity
ammunition cartridges used with standard rifles having standard
rifle twist rates.
BACKGROUND OF THE INVENTION
[0003] Modern firearms use a cartridge which includes a casing that
houses a quantity of propellant, a primer, and a projectile. The
design and configuration of ammunition cartridges have changed
little over the last 75 years. Cartridges are typically designed to
propel projectiles at supersonic velocities, i.e. at a muzzle
velocity greater than approximately 1086 ft/sec. at sea level under
standard conditions of temperature and pressure. The faster a
projectile travels, the flatter is its trajectory to its target.
Also faster projectile speeds tend to reduce the effects of lateral
wind forces upon the projectile path to its target. Therefore, it
has been the practice of firearm and ammunition manufacturers to
maximize the quantity of propellant used to propel the projectile,
consistent with the permissible pressure for a given weapon, as a
means of increasing projectile velocity and accuracy.
[0004] Projectiles traveling at supersonic speeds generate a
noticeable and traceable supersonic crack during their free flight
to the target. This sound, and/or the sound generated by the
projectile breaking the sound barrier, can be used to locate the
source of the weapon from which the projectile was fired. In
military, law enforcement, and covert operations, there is often a
need to conceal the location of shooters and sniper positions. The
use of suppressors (silencers) are important to mask sound and in
some instances location of the shooter. However, most modern
cartridges still have a noticeable and traceable supersonic crack
that cannot be masked by the use of a suppressor. One partial
solution to this problem is to restrict the speed of travel of the
projectile to a subsonic speed.
[0005] For many years gun and ammunition manufacturers have
attempted to produce subsonic ammunition that will perform reliably
and accurately in conventional firearms. It is highly undesirable
to require specially modified firearms suitable for only subsonic
ammunition. Subsonic ammunition cartridges should be
interchangeable with supersonic rounds and fit properly in the same
firearm chamber. The typical approach by manufacturers is to reduce
the quantity of propellant charge in the cartridge. However, this
approach has not worked for several reasons.
[0006] When the quantity of propellant is reduced relative to the
total volume within the cartridge case, inconsistent propellant
ignition can result. This inconsistency is due to the charge being
inconsistently positioned inside the case relative to the primer.
For example, when shooting downward, the propellant may move
forward in the cartridge case, away from the primer, affecting
propellant ignition, pressure, and resulting projectile velocity.
In contrast, when shooting upward, the propellant may move rearward
in the cartridge case, towards the primer, which also affects
propellant ignition, pressure, and projectile velocity. Thus,
propellant ignition and projectile velocity is inconsistent and
unreliable when one simply reduces the quantity of propellant in a
given cartridge volume.
[0007] Several solutions to this problem have been proposed in the
art, including the addition of inert and consumable filler
materials to the propellant, expandable inner sleeves that occupy
the empty cartridge space (U.S. Pat. No. 4,157,684), an inner tube
of propellant inserted within the cartridge (U.S. Pat. No.
6,283,035), a molded foam filler to reduce the internal casing
volume (U.S. Pat. No. 5,770,815), and multiple stepped down stages
in the discharge end of the cartridge casing to reduce the internal
casing volume (U.S. Pat. No. 5,822,904).
[0008] Another problem with reducing the quantity of propellant is
the inability of the ammunition to cycle the firing mechanisms of
fully automatic and semi-automatic weapons. For automatic weapons
to properly cycle, the propellant charge must produce sufficient
gas pressure to accelerate the projectile and to cycle the firing
mechanism. Typical chamber pressures will be in the range from
35,000 psi to 55,000 psi. With a reduced quantity of propellant,
subsonic ammunition generally fails to produce sufficient pressure
to accelerate the projectile and to properly cycle the firing
mechanism of automatic weapons.
[0009] Yet another significant problem with subsonic ammunition is
inaccurate performance. The projectile should exhibit stable flight
under subsonic conditions. While standard rifles and projectiles
are designed for stable supersonic flight, it is often not possible
to achieve stable subsonic flight utilizing a standard projectile
and typical rifling in rifle barrels. Standard rifle projectiles
fired at subsonic velocities tend to tumble in flight, which
results in extremely poor performance.
[0010] It will be appreciated that there is a need in the art for
subsonic ammunition that is accurate, consistent, and reliable,
that can use conventional cartridge loading equipment, that can use
standard cartridges designed for standard firearm chambers and
standard rifle barrels. It would also be an advancement in the art
to provide subsonic ammunition that is able to cycle the firing
mechanisms of automatic weapons.
SUMMARY OF THE INVENTION
[0011] The invention is drawn to ammunition cartridges or rounds
that can be fired through a standard rifle with a common twist rate
at subsonic and reduced velocities. The invention uses standard
rifle cartridges, which include centerfire rifle cartridges
generally recognized as being fired from standard rifles. "Cycling"
subsonic ammunition is specifically designed to cycle the firing
and loading mechanisms of fully automatic and semiautomatic
weapons. "Standard" subsonic ammunition is not designed to cycle
automatic and semiautomatic weapons. Both standard and cycling
subsonic ammunition may be used with "standard rifles" or common,
commercially available rifles. Unlike the prior art, the present
invention does not modify the standard rifle cartridge shape and
does not include cartridge inserts, fillers, elongated projectiles,
or other structures to reduce the cartridge case volume.
[0012] Non-conventional powders (propellants) and projectiles
stable at subsonic or reduced velocity are used with the subsonic
ammunition within the scope of the present invention.
"Non-conventional powders" are powders not typically used in the
selected rifle cartridge. Moderately fast-burning pistol propellant
may be used in the "standard" subsonic ammunition. A slow burning
cannon propellant may be used in the "cycling" subsonic ammunition.
Such propellants are not known for use with small arms ammunition.
Computer software may be used to simulate propellant ballistic
properties in a given cartridge. This can help in selecting and
pre-screening a suitable propellant and determining the quantity of
propellant. The propellant powder is preferably spherical powder to
facilitate accurate dispensing in automatic loading equipment.
[0013] The projectiles are selected to be stable at subsonic or
reduced velocities and at the standard rifle twist rate for the
given rifle cartridge caliber. One or more commercially available
bullet stability calculator may be used to assist in preliminary
projectile selection and screening. The final selection and
optimization can only be made after laboratory and field
testing.
[0014] Without being bound by theory, projectiles with ratios (D:L)
of approximately one are generally stable at subsonic and reduced
velocity. In addition, projectiles in which the center of mass is
approximately equal to the midpoint of the projectile tend to be
more stable at subsonic and reduced velocity. Other projectiles may
be made more stable by moving the center of pressure behind the
center of mass. This may be accomplished by introducing drag to the
rear of the projectile. In addition, the rifle twist rate affects
projectile selection. For example, a broader variety of projectiles
are stable at higher twist rates. Fewer projectiles are stable when
fired from low twist rate rifles.
[0015] Cycling subsonic projectiles are generally heavier
projectiles with a longer bearing surface for increased drag within
the bore and gas seal in the barrel. In this way, the projectile is
expelled more slowly. Instead of using moderately fast burning
pistol propellants, extremely slow burn rate propellants, such as
cannon powders, are used. The slow burning propellant combined with
a heavy, slower projectile result in a longer resident time within
the rifle bore. This keeps pressure high enough to expel the
projectile at subsonic velocities and still cycle actions.
[0016] The foregoing subsonic ammunition within the scope of the
present invention is highly accurate at a range up to about 200-800
yards, depending on the caliber.
[0017] The subsonic ammunition cartridges within the scope of the
present invention may include cartridge casings that have been
colored to identify them as subsonic ammunition. The cartridge
casings may receive a color coating by electroplating or other
durable coating technique. Black is a particularly preferred color,
but other colors, such as olive green, brown, silver, gray or white
may be used.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The invention is drawn to ammunition cartridges or rounds
that can be fired through a standard rifle with a common twist rate
at subsonic and reduced velocities. Two types of subsonic and
reduced velocity ammunition are disclosed herein and identified as
"standard" subsonic ammunition and as "cycling" subsonic
ammunition. Both standard and cycling subsonic ammunition may be
used with standard rifles, but cycling subsonic ammunition is
specifically designed to cycle the firing and loading mechanisms of
fully automatic and semiautomatic weapons.
[0019] As used herein, the term "standard rifle" refers to common,
commercially available rifles. As used herein, the term "standard
rifle cartridge casing" refers to centerfire rifle cartridge
casings generally recognized as being fired from standard rifles
and comprising unmodified brass. As used herein, the term "standard
supersonic ammunition" refers to common, commercially available
rifle ammunition using standard rifle cartridge casings designed to
fire projectiles as supersonic velocity. Examples of typical
standard rifle cartridge casings are identified in published
cartridge reloading handbooks, such as Hornady Handbook of
Cartridge Reloading. A list of some standard rifle cartridges is
set forth in Table 1. It will be appreciated that Table 1 is not
intended to be an exhaustive list of all possible rifle cartridges
that may be used with the present invention and that the present
invention is not limited to the rifle cartridges set forth in Table
1.
1TABLE 1 Some Standard Rifle Cartridges 17 Mach IV 6.5 mm Rmington
Magnum 17 Remington 264 Winechester Magnum 22 Hornet 270 Weatherby
Magnum 22 K-Hornet 7-30 Waters 218 Bee 7 mm-08 Remington 222
Remington 7 .times. 57 mm Mauser 223 Remington 284 Winchester 5.56
.times. 45 mm NATO 280 Remington 222 Remington Magnum 7 mm Express
Remington 22 PPC 7 .times. 65 mm R 5.6 .times. 50 mm Magnum 7
.times. 61 mm, Sharpe & Hart 219 Donaldson Wasp 7 mm Remington
Magnum 219 Zipper 7 mm Weatherby Magnum 225 Winchester 7 mm Dakota
224 Weatherby Magnum 7 mm STW 22-250 Remington 30 M1 Carbone 220
Swift 30-30 Winchester 5.6 .times. 57 mm RWS 7.5 .times. 54 mm MAS
5.6 .times. 52 mm R (22 Savage High Power) 300 Savage 6 .times. 47
mm 307 Winchester 6 mm PPC 7.62 .times. 51 mm NATO 6 mm BR 7.62 mm
Russian 243 Winchester 7.62 .times. 54 mm R 6 mm Remington 7.62
.times. 53 mm R 6 mm-284 30-40 Krag 240 Weatherby Magnum 30-06
25-20 WCF M1 Garand 256 Winchester Magnum 300 H&H Magnum 25-35
Winchester (25 Remington) 308 Norma Magnum 250-300 Savage 300
Winchester Magnum 257 Roberts 300 Weatherby Magnum 257 Roberts
Improved 300 Dakota 25-06 Remington 300 Remington Ultra Mag- num
257 Weatherby Magnum 30-378 Weatherby Magnum 6.5 mm Japanese 32-20
Winchester (32-20 WCF) 6.5 mm Carcano 7.62 .times. 39 mm, M43 6.5
.times. 54 mm Mannlicher-Schoenauer 7.65 mm Belgian Mauser 6.5
.times. 55 mm Swedish Mauser 303 British 260 Remington 7.7 mm
Japanese 6.5 .times. 57 mm 32 Winchester Special 6.5 mm-284 8 mm
Mauser (8 .times. 57 mm S) 6.5 mm-06 8 mm-06 8 .times. 68 mm S 376
Steyr 8 mm Remington Magnum 375 H&H Magnum 33 Winchester 375
Dakota 338-06 378 Weatherby Magnum 338 Winchester Magnum 416 Rigby
330 Dakota 416 Remington 340 Weatherby Magnum 416 Dakota 338 Lapua
Magnum 416 Weatherby Magnum 338-378 Weatherby Magnum 44-40 (Rifle)
348 Winchester 44 Remington Magnum (Rifle) 357 Magnum (Rifle) 444
Marlin 35 Remington 45 Long Colt (Rifle) 358 Winchester 45-70 (Trap
Door) 350 Remington Magnum 45-70 Marlin (1895) 35 Whelen 45-70
Ruger 358 Norma Magnum 458 Winchester Magnum 38-55
Winchester/Ballard 460 Weatherby Magnum 375 Winchester 50 BMG
[0020] The subsonic ammunition within the scope of the present
invention use modern non-conventional powders and carefully
selected projectiles to assure stabilized flight and avoid damage
to suppressor baffles. The term "non-conventional powder" refers to
powder, or propellant, that is not typically used in the selected
rifle cartridge. For example, typical moderately fast burning
pistol propellant may be used in the "standard" subsonic ammunition
within the scope of the present invention. The "cycling" subsonic
ammunition within the scope of the present invention uses neither
pistol nor rifle propellant. Instead, a cannon propellant is used
that has a burn rate slower than conventional pistol and rifle
propellants.
[0021] The projectiles used with the subsonic ammunition within the
scope of the present invention are carefully selected to be stable
at subsonic or reduced velocities and at the standard rifle twist
rate for given cartridge caliber. For example, a typical rifle that
fires a .223 caliber cartridge has a rifle twist rate of one turn
in 9 inches, which is a relatively moderate twist rate. In
contrast, a typical rifle that fires a .308 caliber cartridge has a
rifle twist rate of one turn in 12 inches, which is a relatively
slow twist rate.
[0022] The subsonic ammunition according to the present invention
may be used with a sound suppressor to lower firing decibel levels
and virtually eliminate a sound signature. Unlike known subsonic
ammunition cartridges, the subsonic ammunition within the scope of
the present invention avoids harmful fillers, special cartridge
inserts, cartridge shape modifications, and elongated projectiles
that reduce case volume or pack propellant against the primer flash
hole, thereby presenting no risk of damage to the firearm. These
subsonic rounds are pleasant for the recreational shooter and
provide a significant advantage in tactical situations where
stealth is a requirement.
[0023] Projectile Selection
[0024] There are several tools and resources that may be used to
screen and select a suitable projectile that is stable at subsonic
or reduced velocity and with standard rifle twist rates. For
example, there are many bullet stability calculators available
commercially that take into consideration velocity, bullet length,
bullet weight, barrel rate of twist, and projectile diameter that
can aid in determining bullet stability. One such bullet stability
calculator is titled "Load From a Disk" version 3.0.3 (32bit),
Copyright 1996-2001 Wayne Blackwell and Intelligration Systems
Group. This software was used to select a projectile for a .223
Remington subsonic cartridge. A Hornady 55 grain FMJ-BT/WC
projectile was initially selected for testing with the software.
The projectile dimensions (bullet length of 0.735 inches and bullet
diameter of 0.224 inches), weight (55 grains), the existence of a
boat tail base, and the desired muzzle velocity of 1070 feet per
second (fps), were entered into the software. The program
calculated that this projectile would be stable with an optimum
twist rate of 1 turn in 9 inches and a bullet rate of spin of
(rev/sec) 1426. Since the standard twist rate for a .223 Remington
is 1 turn in 9 inches, this software indicated that the Hornady 55
grain FMJ-BT/WC (full metal jacket, boat tail, with cannelure)
projectile will stabilize in commercially available firearms at
subsonic velocities.
[0025] Another useful bullet stability calculator is the National
Firearms Association Bullet Stability Calculator, (Copyright 2002
National Firearms Association, Box 52183, Edmonton, Alberta, T6G
2T5 Canada) available on the internet at
http://www.nfa.ca/NFAFiles/CFJArchive/Ballis-
tics/BulletStabilityCalc.html. This program may be used to select a
projectile for .308 Winchester subsonic cartridge. A Hornady 170.0
grain RN (round nose) projectile was initially selected for testing
with the software. The following data was entered into the program:
the velocity of 1070 fps, bullet length of 0.95 inches, bullet
weight of 170 grains, standard rifle twist of commercially
available .308 Winchester firearms (one turn in 12 inches), and the
diameter of the bullet 0.308 inches. The program then calculates
the stability factor of 3.89. A stability factor greater than 1.5
is considered to be stable.
[0026] Other known bullet stability calculators are available from
Corbin Software, PO Box 2171, 600 Industrial Circle, White City,
Oregon 97503 and online at
http://www.lascruces.com/.about.jbm/ballistics/calculations-
.html.
[0027] The foregoing stability calculators are intended to provide
an initial screening of projectiles that might be used in subsonic
ammunition. It is recommended to test a given projectile using more
than one stability calculator. The final selection and optimization
can only be made after laboratory and field testing.
[0028] Without being bound by theory, it is presently believed that
suitable projectiles may be initially selected based on ratios of
Diameter and Length. Projectiles with ratios (D:L) of approximately
one are better suited for subsonic and reduced velocity
projectiles. In addition, projectiles in which the center of mass
is approximately equal to the midpoint of the projectile tend to be
more stable at subsonic and reduced velocity. Such projectiles may
have round or flat points. In addition, the rifle twist rate
affects projectile selection. For example, a broader variety of
projectiles are stable at higher twist rates. Fewer projectiles are
stable when fired from low twist rate rifles.
[0029] Also without being bound by theory, another method of
stabilizing a projectile is to move the center of pressure behind
the center of mass or what is commonly referred to as the center of
gravity or CG. One possible way to accomplish this is introducing
drag to the rear of the projectile. Introducing angles over 7
degrees on the boat tail is one possible way. In other words, boat
tail angles between 7 and 90 degrees will introduce more drag to
the rear of the projectile. A boat tail angle of 90 degrees is
equivalent to a flat projectile base. Discontinuities of the rear
portion of the bullet can increase drag.
[0030] Propellant Selection
[0031] Propellant or powder selection is important in subsonic
ammunition. Firearm manufacturers have set pressure limitations on
firearm assemblies. By using fillers or reducing charge volumes of
standard propellants to obtain subsonic velocities, pressure can
exceed firearm ratings and cause dangerous situations. Therefore, a
high level of skill is required to safely use reduced propellant
charges.
[0032] For standard subsonic ammunition in accordance with the
present invention, the propellant may be a moderately fast burning
powder, such as a standard pistol powder, to generate adequate
pressure to overcome the forces associated with case neck release
and initial rifling engagement forces. The term "moderately fast
burning powder" is not intended to embrace the very fastest pistol
powders. Similarly, it is to be distinguished from fast rifle
powders. This is accomplished while retaining just enough pressure
to allow the projectile to overcome remaining drag in the bore as
well as any gas relief characteristics of firearms and still
maintaining subsonic velocities.
[0033] Table 2 is a typical propellant bum rate chart. The
information is drawn from the internet website,
http://www.reloadammo.com/burnrate.htm (M. D. Smiths Reloading
Pages). The chart is courtesy of Hodgdon Powder Company. Table 1
lists qualitative bum rates from fastest to slowest. The actual
quantitative burn rate of these propellants is generally
proprietary information. Nevertheless, the propellants 1-41 are
typically used for pistols and shotgun applications, propellants
42-80 are typically used for small to medium centerfire rifle
applications, and propellants 81-107 are typically used for large
and magnum centerfire rifle applications. The table is for general
information only and one can not assume that each step is
incremental in the chart.
2TABLE 2 Propellant Burn Rate Chart (List from Fastest to Slowest
Propellant) 1. R-1 Norma 2. N310, Vihtavuori 3. Bullseye, Alliant
4. N312, Vihtavuori 5. Solo 1000, Accurate 6. Clays, Hodgdon 7. Red
Dot, Alliant 8. N318, Vihtavuori 9. Hi-Skor 700X, IMR 10. N320,
Vihtavuori 11. Green Dot, Alliant 12. International, Hodgdon 13.
No. 2, Accurate 14. N321, Vihtavuori 15. N324, Vihtavuori 16.
HP-38, Hodgdon 17. W-231, Winchester 18. N325, Vihtavuori 19. N330,
Vihtavuori 20. PB, IMR 21. N331, Vihtavuori 22. No. 5, Accurate 23.
Unique, Alliant 24. WSL, Winchester 25. Power Pistol, Alliant 26.
Universal, Hodgdon 27. SR-7625, IMR 28. W-473AA, Winchester 29.
Herco, Alliant 30. N340, Vihtavuori 31. WSF, Winchester 32. HS-6,
Hodgdon 33. W-540, Winchester 34. 3N37, Vihtavuori 35. WAP,
Winchester 36. Hi-Skor 800-X, IMR 37. N350, Vihtavuori 38. HS-7,
Hodgdon 39. W-571, Winchester 40. No. 7, Accurate 41. Blue Dot,
Alliant 42. No. 9, Accurate 43. 2400, Alliant 44. N110, Vihtavuori
45. R-123, Norma 46. H-110, Hodgdon 47. W-296, Winchester 48.
SR-4759, IMR 49. N120, Vihtavuori 50. XMP-5744, Accurate 51.
IMR-4227, IMR 52. N125, Vihtavuori 53. H-4227, Hodgdon 54. N130,
Vihtavuori 55. AAC-1680, Accurate 56. W-680, Winchester 57. N132,
Vihtavuori 58. N-200 Norma 59. N133, Vihtavuori 60. IMR-4198, IMR
61. H-4198 Hodgdon 62. XMR-2015, Accurate 63. Reloader 7, Alliant
64. N134, Vihtavuori 65. IMR-3031, IMR 66. Benchmark 1, Hodgdon 67.
N-201, Norma 68. H-322, Hodgdon 69. Benchmark2 , Hodgdon 70.
AAC-2230, Accurate 71. IMR-4895, IMR 72. H-4895, Hodgdon 73. H-335,
Hodgdon 74. BL-C(2), Hodgdon 75. AAC-2460, Accurate 76. W-748,
Winchester 77. Reloader 12, Alliant 78. N135, Vihtavuori 79.
IMR-4064, IMR 80. Varget, Hodgdon 81. AAC-2520, Accurate 82. N-202,
Norma 83. XMR-4064, Accurate 84. IMR-4320, IMR 85. N140, Vihtavuori
86. AAC-2700, Accurate 87. Reloader 15, Alliant 88. H-380, Hodgdon
89. N150, Vihtavuori 90. W-760, Winchester 91. H-414, Hodgdon 92.
N160, Vihtavuori 93. IMR-4350, IMR 94. H-4350 Hodgdon 95. N-204,
Norma 96. Reloader 19, Alliant 97. IMR-4831, IMR 98. XMR-3100,
Accurate 99. H-450, Hodgdon 100. H-4831, Hodgdon 101. MRP, Norma
102. N165, Vihtavuori 103. Reloader 22, Alliant 104. IMR-7828, IMR
105. H-1000, Hodgdon 106. XMR-8700, Accurate 107. H-870,
Hodgdon
[0034] Computer software may be used to simulate propellant
ballistic properties in a given cartridge. This can help in
selecting and pre-screening a suitable propellant and determining
the quantity of propellant. One such program is called
"QuickLOAD--Interior Ballistics Predictor Program" (Copyright
1987-2001 -H. Broenel, Babenhausen Germany), distributed by
Nostalgia Enterprises Company, aka NECO, 536C Stone Road, Benicia,
Calif. 94510, http://www.neconos.com/index.html. The software
includes data on more than 800 cartridges, 140 powders, and 2000
bullets. Data on other cartridges, powders, and bullets may be
manually entered. To use the software, one selects the cartridge,
the projectile, and the powder charge. The software will predict
muzzle velocity and chamber pressure. It will graph pressure and
velocity with respect to barrel position. It can also provide other
information, such as the bullet's travel at the time of maximum
pressure. It is important to recognize that such ballistic
simulation software cannot predict catastrophic events, like using
low charges of standard powders accurately, or using extremely fast
powders. But the software is useful to provide initial selection
and screening, and to provide information on the quantity of
propellant to be used. The final selection and optimization is done
through field-testing with strain gauges to measure chamber
pressure and a chronograph to measure actual velocity.
[0035] Several different standard subsonic cartridge assemblies
have been prepared, which include, but are not limited to:
[0036] 1. .223 cartridge--PMC brass, Winchester small rifle primer,
3.9 grains Alliant Unique, Hornady 55 grain FMJ-BT W/C projectile,
Cartridge overall length=2.24 inches.
[0037] 2. .223 cartridge--PMC brass, Winchester small rifle primer,
4.2 grains WP-1450, Hornady 55 grain Moly FMJ-BT W/C projectile,
Cartridge overall length=2.24 inches.
[0038] 3. .308 cartridge--PMC brass, Winchester large rifle primer,
8.2 grains Alliant Unique, Hornady 170 grain FP projectile,
Cartridge overall length=2.565 inches.
[0039] 4. .308 cartridge--PMC brass, Winchester large rifle primer,
8.5 grains WP-1450, Hornady 170 grain RN projectile, Cartridge
overall length=2.565 inches.
[0040] 5. .300 Winchester Magnum cartridge--PMC brass, Winchester
large rifle primer, 14.0 grains Alliant Unique, Nossler 220 grain
SSP projectile, Cartridge overall length=3.332 inches.
[0041] 6. 7.62.times.39 mm cartridge--PMC brass, Winchester large
rifle primer, 7.8 grains Alliant Unique, Sierra 180 grain Spitzer
projectile, Cartridge overall length=2.19 inches.
[0042] 7. .50 BMG cartridge--IMI brass, CCI# 35 primer, 35.0 grains
WC-1450 [SHOULD IT BE WP-1450?], 647.0 grain FMJ, Cartridge overall
length=5.45 inches.
[0043] In general terms, a typical standard subsonic .223 caliber
rifle cartridges will contain from 3.5 to 4.5 grains of moderately
fast pistol propellant and a projectile weighing from 50 to 60
grains. A typical, a standard subsonic .308 caliber rifle cartridge
will contain from 6 to 9 grains of pistol propellant and a
projectile weighing from 150 to 220 grains. A typical standard
subsonic .50 BMG rifle cartridge will contain from 20 to 60 grains
of moderately fast pistol propellant and a projectile weighing from
525 to 900 grains. A typical standard subsonic .300 Winchester
Magnum rifle cartridge will contain from 8 to 16 grains of
moderately fast pistol propellant and a projectile weighing from
150 to 230 grains. A typical standard subsonic 7.62.times.39 mm
rifle cartridge will contain from 7.5 to 8.5 grains of moderately
fast pistol propellant and a projectile weighing from 170 to 190
grains. Generally, the smaller weight projectile would be used will
less propellant.
[0044] By way of comparison, a standard supersonic .223 rifle
cartridge contains about 25 grains of propellant. The standard
subsonic .223 rifle cartridge within the scope of the present
invention contains about 3.5 to 4.5 grains of a moderately fast
burning pistol propellant, or about 20%, by weight of the rifle
propellant used in a comparable standard supersonic rifle
cartridge. In general terms, the standard subsonic ammunition
within the scope of the present invention will contain a moderately
fast burning pistol propellant which is from about 15% to about
20%, by weight, of the rifle propellant used in a comparable
standard supersonic rifle cartridge.
[0045] Surprisingly, the reduced quantity of propellant used with
the standard subsonic ammunition does not exhibit inconsistent
ignition. Unlike prior art attempts, the subsonic ammunition in
accordance with the present invention does not require special
cartridge inserts, fillers, or casing modifications. Without being
bound by theory, it is believed the small quantity of propellant
used in the standard subsonic produces consistent ballistic
performance with a reduced propellant charge because the propellant
undergoes substantially complete combustion within the cartridge
casing. In other words, the small quantity of moderately fast
burning pistol propellant generates enough gas pressure within the
casing off of the initial primer flash to fill the casing with
pressure. Sufficient pressure is generated within the casing to
expel the projectile at subsonic or reduced velocity.
[0046] When fired, the foregoing projectiles traveled at velocities
less than 1100 feet per second. The accuracy and penetrating
performance of subsonic ammunition prepared according to the
above-identified specifications were evaluated:
[0047] 1. A .223 subsonic cartridge fired from 16 inch M16 with AWC
Raider sound suppressor penetrated level III A body armor at 25
yards and 100 yards.
[0048] 2. A .308 subsonic cartridge fired from 20 inch Remington
PSS bolt action rifle with AWC Thundertrap sound suppressor
penetrated level III A body armor at 25 yards and 100 yards.
[0049] 3. A .300 Winchester Magnum cartridge fired from 26 inch
HS-Precision bolt action rifle with AWC Thundertrap sound
suppressor penetrated level III A body armor at 25 yards and 100
yards.
[0050] 4. A .223 subsonic cartridge fired from Remington PSS bolt
action rifle with AWC Thundertrap sound suppressor accomplished
Minute Of Angle "MOA" at 100 yards.
[0051] 5. A .308 subsonic cartridge fired from Remington PSS bolt
action rifle with AWC Thundertrap sound suppressor accomplished
Minute Of Angle "MOA" at 100 yards.
[0052] 6. A .300 Win Mag subsonic cartridge fired from 26 inch
HS-Precision bolt action rifle with AWC Thundertrap sound
suppressor accomplished Minute Of Angle "MOA" at 100 yards.
[0053] The foregoing subsonic ammunition provide accurate
projectile trajectory at a range up to about 200-800 yards,
depending on the caliber. Lighter projectiles, such as those used
with the .223 caliber cartridge, have a shorter range. Heavy
projectiles can maintain velocity and accuracy longer.
[0054] Cycling subsonic projectiles are selected to be stable at
subsonic and reduced velocity using the process described above.
However, they are generally heavier projectiles with a longer
bearing surface for increased drag within the bore and gas seal in
the barrel. In this way, the projectile is expelled more slowly.
Lighter projectiles may be used if the brass is crimped about the
projectile. If very heavy projectiles are used, such as depleted
uranium projectiles, a shorter bearing surface may be used.
[0055] Instead of using moderately fast burning pistol propellants,
extremely slow burn rate propellants, such as cannon powders, are
used. The slow burning propellant combined with a heavy, slower
projectile result in a longer resident time within the rifle bore.
This keeps pressure high enough to expel the projectile at subsonic
velocities and still cycle the action. A light projectile used with
slow burning propellant would likely get stuck in the barrel.
[0056] Several different standard subsonic cartridge assemblies
have been prepared, which include, but are not limited to:
[0057] 1. .223 cartridge--PMC brass, Winchester small rifle primer,
24 grains WP-1840 powder, custom 106 grain projectile (diameter of
0.224 inches, bearing surface of 0.825 inches, overall length of
1.078 inches), Cartridge overall length=2.21 inches.
[0058] 2. .223 cartridge--PMC brass, Winchester small rifle primer,
18.5 grains WP-1850 powder, custom 106 grain projectile (diameter
of .224 inches, bearing surface of 0.825 inches, overall length of
1.078 inches), Cartridge overall length=2.21 inches.
[0059] A typical cycling subsonic .223 caliber rifle cartridge will
contain from 18 to 25 grains of cannon propellant and a projectile
weighing from 90 to 125 grains. The projectile bearing surface may
range from 0.4 to 1.1 inches, and preferably from 0.8 to 0.9
inches. Less bearing surface is needed if the projectile is crimped
in position. Also, heavy projectiles require less bearing
surface.
[0060] It will be appreciated that different powders, projectiles,
and primers may be substituted for those identified above. For
example, the powder "Alliant Unique," which is number 23 in Table
2, is a flake propellant. Flake propellant does not dispense well
in automatic loading equipment, or at least at the accuracy
tolerances needed to prepare reliable subsonic ammunition in
accordance with the present invention. Western Powder WP-1450 is a
spherical powder having ballistic properties comparable to Alliant
Unique powder. The spherical powder dispenses accurately in
automatic loading equipment; the powder selected is preferably a
spherical powder. Similarly, the cycling subsonic ammunition
examples identified above used WP-1840 and WP-1850 powders, which
are spherical powders. A comparable, alternative powder is H-4831,
Hodgdon, number 100 in Table 2. Another alternative powder is
H-4831SC is not listed in Table 2. H-4831SC is similar to H-4831,
except that it is less susceptible to changes in temperature.
H-4831 and H-4831SC are extruded propellants that will not dispense
well in automatic loading machines. But such propellants could
still be used to prepare subsonic ammunition.
[0061] The subsonic ammunition cartridges within the scope of the
present invention may include cartridge casings that have been
colored to identify them as subsonic ammunition. The cartridge
casings may receive a color coating by electroplating or other
durable coating technique. Black is a particularly preferred color,
but other colors, such as olive green, brown, silver, gray or white
may be used.
[0062] It will be appreciated that the present invention provides
subsonic ammunition that is accurate, consistent, and reliable,
that can use conventional cartridge loading equipment, that can use
standard cartridges designed for standard firearm chambers and
standard rifle barrels. The present invention also provides
subsonic ammunition that is able to cycle the firing mechanisms of
automatic and semi-automatic weapons.
[0063] The present invention may be embodied in other specific
forms without departing from its essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description.
* * * * *
References