U.S. patent application number 12/800879 was filed with the patent office on 2011-12-01 for subsonic small-caliber ammunition and bullet used in same.
This patent application is currently assigned to Engel Ballistic Research. Invention is credited to Phil Backman, John Whitworth Engel, Christopher Bernard Luchini.
Application Number | 20110290141 12/800879 |
Document ID | / |
Family ID | 45021005 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110290141 |
Kind Code |
A1 |
Engel; John Whitworth ; et
al. |
December 1, 2011 |
Subsonic small-caliber ammunition and bullet used in same
Abstract
A bullet for use with a small caliber rifle comprises a jacket
and a lead core provided within the jacket. The jacket is drawn
from a copper alloy material. A bearing surface portion of the
jacket has a nominal thickness less than about .010'' and the
copper alloy material of at least the bearing surface portion of
the jacket has a nominal hardness that is substantially greater
than an as-drawn hardness of the copper alloy material of the
bearing surface portion of the jacket.
Inventors: |
Engel; John Whitworth;
(Smithville, TX) ; Luchini; Christopher Bernard;
(Los Alamos, NM) ; Backman; Phil; (Koo Wee Rup,
AU) |
Assignee: |
Engel Ballistic Research
|
Family ID: |
45021005 |
Appl. No.: |
12/800879 |
Filed: |
May 25, 2010 |
Current U.S.
Class: |
102/439 ;
102/514; 86/55 |
Current CPC
Class: |
F42B 30/02 20130101;
F42B 12/74 20130101; F42B 5/16 20130101; F42B 12/78 20130101 |
Class at
Publication: |
102/439 ;
102/514; 86/55 |
International
Class: |
F42B 5/02 20060101
F42B005/02; F42B 30/02 20060101 F42B030/02 |
Claims
1. A bullet for use with a small caliber rifle, comprising: a
jacket drawn from a copper alloy material, wherein a bearing
surface portion of the jacket has a nominal thickness less than
about 0.010'' and wherein the copper alloy material of at least the
bearing surface portion of the jacket has a nominal hardness that
is substantially greater than an as-drawn hardness of the copper
alloy material of the bearing surface portion of the jacket; and a
lead core provided within the jacket.
2. The bullet of claim 1 wherein the bearing surface portion of the
jacket is at least partially coated with a friction-reducing
material composition.
3. The bullet of claim 2 wherein the friction-reducing material
composition is molybdenum disulfide.
4. The bullet of claim 3 wherein the bearing surface portion is
coated in its entirety with the friction-reducing material
composition.
5. The bullet of claim 1 wherein the nominal hardness of the copper
alloy material of at least bearing surface portion corresponds to a
tensile strength of between about 32 ksi and about 44 ksi.
6. The bullet of claim 5 wherein the bearing surface portion of the
jacket is at least partially coated with a friction-reducing
material composition.
7. The bullet of claim 6 wherein the friction-reducing material
composition is molybdenum disulfide.
8. The bullet of claim 7 wherein the bearing surface portion is
coated in its entirety with the friction-reducing material
composition.
9. The bullet of claim 5 wherein the bearing surface portion of the
jacket has a thickness between about 0.004'' and about 0.008''.
10. The bullet of claim 1 wherein the bearing surface portion of
the jacket has a thickness between about 0.004'' and about
0.008''.
11. A round of ammunition configured for providing sufficient
energy for cycling a bolt carrier in a rifle having a gas-energized
bolt carrier actuation mechanism, comprising: a small-caliber
cartridge casing configured in accordance with an original
equipment manufacturer (OEM) specification for the rifle; a bullet
having a bearing surface portion thereof engaged within a bullet
receiving opening of the small-caliber cartridge casing thereby
forming a propellant-receiving cavity within the small-caliber
cartridge casing, wherein the bullet has a core made of a metal
having lead as its major constituent component and a jacket drawn
from metal having copper as its major constituent component,
wherein a nominal thickness of the jacket is less than about
0.010'', and wherein at least the bearing surface portion of the
jacket has a nominal hardness that is substantially greater than an
as-drawn hardness of the jacket; and a propellant within the
propellant-receiving cavity of the small-caliber cartridge casing,
wherein the propellant is configured by a manufacturer thereof for
being used in medium caliber ammunition.
12. The round of ammunition of claim 11 wherein the bearing surface
portion of the jacket is at least partially coated with a
friction-reducing material composition
13. The round of ammunition of claim 12 wherein the
friction-reducing material composition is molybdenum disulfide.
14. The round of ammunition of claim 13 wherein the bearing surface
portion is coated in its entirety with the friction-reducing
material composition.
15. The round of ammunition of claim 11 wherein the nominal
hardness of said jacket metal of at least the bearing surface
portion corresponds to a tensile strength of between about 32 ksi
and about 44 ksi.
16. The round of ammunition of claim 15 wherein the bearing surface
portion of the jacket is at least partially coated with a
friction-reducing material composition.
17. The round of ammunition of claim 16 wherein the
friction-reducing material composition is molybdenum disulfide.
18. The round of ammunition of claim 17 wherein the bearing surface
portion is coated in its entirety with the friction-reducing
material composition.
19. The round of ammunition of claim 15 wherein the bearing surface
portion of the jacket has a thickness between about 0.004'' and
about 0.008''.
20. The round of ammunition of claim 11 wherein the bearing surface
portion of the jacket has a thickness between about 0.004'' and
about 0.008''.
21. A method for making a bullet for use with a small caliber
rifle, comprising: providing a jacket having a thickness less than
about 0.010'', wherein the jacket is drawn from a copper alloy
material; forming a lead core within a core-receiving cavity of the
jacket; and hardening at least a bearing surface portion of the
jacket to have a nominal hardness that is substantially greater
than an as-drawn hardness of the jacket after forming the lead core
within the core-receiving cavity of the jacket.
22. The method of claim 21 wherein said hardening includes shot
peening the jacket with steel shot.
23. The method of claim 22, further comprising: exposing the jacket
and the steel shot to a friction-reducing material composition
during said shot peening such that said shot peening causes at
least a portion of an exterior surface of the jacket to become
coated with a layer of the friction-reducing material
composition.
24. The method of claim 23 wherein the friction-reducing material
composition is molybdenum disulfide.
25. The method of claim 21 wherein the nominal hardness of the
copper alloy material of at least the bearing surface portion
corresponds to a tensile strength of between about 32 ksi and about
44 ksi after performing said hardening.
26. The method of claim 25 wherein said hardening includes shot
peening the jacket with steel shot.
27. The method of claim 26, further comprising: exposing the jacket
and the steel shot to a friction-reducing material composition
during said shot peening such that said shot peening causes at
least a portion of an exterior surface of the jacket to become
coated with a layer of the friction-reducing material composition.
Description
FIELD OF THE DISCLOSURE
[0001] The disclosures made herein relate generally to ammunition
for firearms and, more particularly, to subsonic ammunition for use
with semi and fully automatic weapons.
BACKGROUND
[0002] The projectile (i.e., bullet) from a fired weapon,
particularly a rifle, typically leaves the muzzle of the weapon at
a speed that is greater than the speed of sound, i.e. a muzzle
velocity of greater than approximately 1086 ft/sec. at sea level
under standard conditions of temperature and pressure. Such a speed
is referred to as being supersonic. Causing the bullet to achieve
supersonic speed is advantageous because the faster a projectile
travels, the flatter is its trajectory to its intended target.
Also, faster speeds of projectiles tend to reduce the effects of
lateral wind forces upon the path of the projectile to its intended
target.
[0003] Due to supersonic speed of a projectile enhancing its
accuracy of delivery to an intended target, it can be seen why it
is desirable for projectiles to have a supersonic muzzle velocity.
However, projectiles travelling at supersonic speeds generate an
audible sound during their free flight, which can undesirably be
used to locate the source of the weapon from which the projectile
was fired. Under certain circumstances of military operations
and/or police operations, it is desirable that the source of the
weapon firing a projectile not be identifiable by the sound
generated by the travelling projectile. Furthermore, for a
projectile of a given shape and mass, it is sometimes desirable for
muzzle velocity to be used in limiting the potential for the
projectile to strike a down-range object in the case with the
projectile misses or passes through its intended target.
[0004] In certain situations, one approach for mitigating adverse
concerns relating to supersonic muzzle velocity is to restrict the
speed of travel of the projectile to a subsonic speed (i.e., a
muzzle velocity of less than approximately 1086 ft/sec. at sea
level under standard conditions of temperature and pressure). In
doing so, the projectile does not generate an audible sound during
its free flight, thus limiting the potential for locating the
source of the projectile. Additionally, subsonic flight reduces the
distance that a projectile can travel, thereby limiting the
potential for the projectile to strike down-range objects.
[0005] In semi-automatic and fully automatic weapons, pressure
(i.e., energy) generated by firing of a round of ammunition serves
to energize the weapon's bolt actuation mechanism. As such,
implementing subsonic flight of a projectile in a manner that
reduces pressure within a weapon's barrel bore can result in there
being insufficient energy generated during combustion of the
ammunition to cycle the bolt in a semi-automatic or fully-automatic
weapon and/or to lock the bolt in its open position upon the firing
of the last round in the weapons' magazine. In some cases, gas
pressure provided at a gas port of a weapon can be increased to
suitable energizes a bolt-actuation mechanism of the weapon through
use of a sound suppressor to sufficient levels. However, removal of
the sound suppressor renders such weapon inoperable in its
semi-automatic and/or automatic modes of operation when such
pressure-deficient rounds of ammunition are used.
[0006] Accordingly, subsonic ammunition that is capable of
providing sufficient energy for cycling the bolt actuation
mechanism of a semi-automatic or fully automatic weapon without the
use of a sound suppressor is advantageous, desirable and
useful.
SUMMARY OF THE DISCLOSURE
[0007] Embodiments of the present invention are directed to bullets
and rounds of ammunition that are configured for use with
small-caliber semi-automatic and automatic weapons. More
specifically, small-caliber bullets and rounds of ammunition
configured in accordance with embodiments of the present invention
provide subsonic flight when discharged in a semi-automatic or
fully-automatic weapon and provide sufficient barrel bore pressure
characteristics for cycling a gas-energized bolt actuation
mechanism of such semi-automatic or fully-automatic weapon without
the use of a sound suppressor to augment gas pressure within the
barrel bore of the weapon. Ammunition configured in accordance with
the present invention is well suited for applications where
firepower is more of a consideration than is stealth. Accordingly,
embodiments of the present invention advantageously overcome one or
more shortcomings associated with some conventional small-caliber
subsonic rounds of ammunition.
[0008] In one embodiment of the present invention, a bullet for use
with a small caliber rifle comprises a jacket and a lead core
provided within the jacket. The jacket is drawn from a copper alloy
material. A bearing surface portion of the jacket has a nominal
thickness less than about 0.010'' and the copper alloy material of
at least the bearing surface portion of the jacket has a nominal
hardness that is substantially greater than an as-drawn hardness of
the copper alloy material of the bearing surface portion of the
jacket.
[0009] In another embodiment of the present invention, a round of
ammunition configured for providing sufficient energy for cycling a
bolt carrier in a rifle having a gas-energized bolt carrier
actuation mechanism comprises a small-caliber cartridge casing, a
bullet having a bearing surface portion thereof engaged within a
bullet receiving opening of the small-caliber cartridge casing
thereby forming a propellant-receiving cavity within the
small-caliber cartridge casing, and a propellant within the
propellant-receiving cavity of the small-caliber cartridge casing.
The small-caliber cartridge casing is configured in accordance with
an original equipment manufacturer (OEM) specification for the
rifle. The bullet has a core made of a metal having lead as its
major constituent component and a jacket drawn from metal having
copper as its major constituent component. A nominal thickness of
the jacket is less than about 0.010''. At least the bearing surface
portion of the jacket has a nominal hardness that is substantially
greater than an as-drawn hardness of the jacket. The propellant is
configured by a manufacturer thereof for being used in medium
caliber ammunition.
[0010] In another embodiment of the present invention, a method for
making a bullet for use with a small caliber rifle comprises
providing a jacket having a thickness less than about 0.010'',
forming a lead core within a core-receiving cavity of the jacket,
and hardening at least a bearing surface portion of the jacket to
have a nominal hardness that is substantially greater than an
as-drawn hardness of the jacket after forming the lead core within
the core-receiving cavity of the jacket. The jacket is drawn from a
copper alloy material.
[0011] These and other objects, embodiments, advantages and/or
distinctions of the present invention will become readily apparent
upon further review of the following specification, associated
drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a side view showing a round of ammunition
configured in accordance with an embodiment of the present
invention.
[0013] FIG. 2 is a fragmentary cross-sectional view of the round of
ammunition of FIG. 1.
DETAILED DESCRIPTION OF THE DRAWING FIGURES
[0014] Referring now to FIGS. 1 and 2, a round of ammunition 100
configured in accordance with the present invention is shown. The
round of ammunition 100 is configured for use with small-caliber
semi-automatic and automatic weapons (e.g., a rifle).
Advantageously, the round of ammunition 100 is configured to
provide subsonic flight when discharged in a semi-automatic or
fully-automatic weapon and to provide sufficient gas pressure
characteristics for cycling a gas-energized bolt actuation
mechanism of such semi-automatic or fully-automatic weapon without
the use of a sound suppressor to augment gas pressure. In doing so,
the round of ammunition 100 advantageously overcomes a key
shortcoming associated with some conventional small-caliber
subsonic rounds of ammunition.
[0015] The round of ammunition 100 includes a small-caliber
cartridge casing 102 configured in accordance with an original
equipment manufacturer (OEM) specification for a weapon. The
small-caliber cartridge casing 102 includes a first end portion 104
and a second end portion 106. Typically, a primer is mounted within
the second end portion 106 thereby making the second end portion
substantially closed. Preferably, but not necessarily, the
small-caliber cartridge casing 102 can be made a metal material
(e.g., brass) or from a polymeric material (e.g., nylon).
[0016] Standards for the shape and size of a cartridge for a
certain weapons of a given caliber have been established and
published by Sporting Arms and Ammunition Manufacturers Institute
(SAAMI). A rifle of the M4/M16/AR15 family of carbine rifles is a
weapon that is capable of being operated in a semi-automatic mode
and/or fully-automatic mode and that utilizes barrel bore pressure
resulting from discharge of a round of ammunition to energize a
bolt actuation mechanism of the weapon. Thus, in one embodiment,
the round of ammunition 100 can be configured for use with a rifle
of the M4/M16/AR15 family of carbine rifles. However, in view of
the disclosures made herein, it is disclosed that a skilled person
will appreciate other weapons for which a round of ammunition
configured in accordance with the present invention will be useful
and that embodiments of the present invention are not unnecessarily
limited to use with any particular weapon (i.e., any particular
rifle, piston, or other type of small-caliber firearm).
[0017] The round of ammunition 100 has a bullet 108 (i.e., a
projectile) with a bearing surface portion 110 engaged within a
bullet receiving opening 112 of the small-caliber cartridge casing
102. The bullet receiving opening 112 is located at the first end
portion 104 of the small-caliber cartridge casing 102. In this
manner, a propellant-receiving cavity 114 is formed within the
small-caliber cartridge casing 102 between its first and second end
portions 104, 106. An ogive portion 116 (i.e., contoured tip
portion) of the bullet 108 extends beyond the bullet receiving
opening 112 and, optionally, some of the bearing surface portion
can also extend beyond the bullet receiving opening 112.
[0018] As shown in FIG. 2, the bullet 108 has a core 118 made of a
first type of metal disposed within a core-receiving cavity 119 of
a jacket 120 made of a second type of metal. A jacket configured in
accordance with the present invention can be made by the process of
drawing metal (e.g., a sheet of metal) into a given shape and the
bearing surface portion 110 can have a thickness of less than about
0.010''. In a preferred embodiment, the bearing surface portion 110
has a nominal thickness between about 0.004'' and about 0.008''.
Preferably, but not necessarily, the jacket 120 is made from a
copper alloy including about 90% copper (Cu) and up to about 10%
zinc (Zn) and the core 118 is made from a metal having lead as its
major constituent component. In a preferred embodiment, the jacket
120 is made from a copper alloy having a minimum of about 2%
zinc.
[0019] The bearing surface portion 110 and, optionally, the ogive
portion 116 have a nominal hardness that is substantially greater
than an as-drawn hardness of the jacket 120. In a preferred
embodiment, the jacket 120 is drawn from a copper alloy material
having a tensile strength substantially below about 32 ksi.
Subsequent to the jacket 120 being drawn and the core 118 being
formed within the core-receiving cavity 119 of the jacket 120, the
bearing surface portion 110 and optionally the ogive portion 116
are hardened to have a tensile strength greater than about 32 ksi.
In a preferred embodiment, the bearing surface portion 110 and
optionally the ogive portion 116 are hardened to have a tensile
strength between about 32 ksi and about 44 ksi. Optionally, the
finished hardness specification for the copper alloy material can
be specified as between about one-eighth hard and about one-half
hard with respect to the copper alloy material being "dead soft".
As such, it is disclosed herein that, after forming the core 118
within the core-receiving cavity 119 of the jacket 120, the bearing
surface portion 110 of the jacket 120 and optionally the ogive
portion 116 preferably have a nominal hardness that is
substantially greater than an as-drawn hardness of the jacket
120.
[0020] Examples of means for hardening the jacket 120 include, but
are not limited to, shot peening, ultrasonic hardening, and the
like. In the case where the jacket is shot peened, the jacket 120
and the shot (e.g., steel shot) can optionally be exposed to a
friction-reducing material composition during such shot peening so
that the shot peening causes at least a portion of an exterior
surface 122 of the jacket 120 to become coated with a layer of
friction-reducing material composition. Molybdenum disulfide is one
example of a friction-reducing material composition (i.e., a
lubricant) to which the jacket 120 and the shot (e.g., steel shot)
can be exposed during such shot peening for causing the exterior
surface of the jacket 120 to become coated with a layer of
friction-reducing material composition (i.e., a layer of molybdenum
disulfide).
[0021] As shown in FIG. 2, the round of ammunition 100 has a
propellant 124 (e.g., powder) within the propellant-receiving
cavity 114. The propellant 124 can be a relatively slow burning
type propellant that provides a rapid peak in pressure build up
within the propellant-receiving cavity 114 and that maintains a
broader burn duration than relatively fast burning type
propellants. In one embodiment, the propellant 124 is configured by
a manufacturer thereof for being used as a medium caliber
ammunition propellant. One example of such a medium caliber
propellant suitable for use with rounds of ammunition configured in
accordance with the present invention has been offered from General
Dynamics Corporation under propellant no. XPR 47C1. In view of the
disclosures made herein, a skilled person will appreciate that
other propellants of suitable specification can be used in rounds
of ammunition configured in accordance with the present
invention.
[0022] During firing of the round of ammunition 100 within a
weapon, the propellant 124 in combination with the bullet 108
result in gas pressure characteristics and bullet-bore frictional
characteristics that provide for subsonic flight of the bullet 108
and for sufficient gas pressure within a barrel bore of the weapon
to cycling a gas-energized bolt actuation mechanism of the weapon.
For a given configuration of ammunition (e.g., 5.56 mm NATO
ammunition), the bullet 108 will be heavier (e.g., by as much as 12
grains) than a bullet with a standard thickness drawn-metal jacket
in view of the relatively thin jacket 120 and greater volume of the
core 118. When this relatively heavy, thin-jacket bullet 108 is
subjected to the heat and pressure of discharge of the propellant
108, the relatively thin jacket 120 and the relatively large core
118 will result in enhanced obturation of the bearing surface
portion 110 of the bullet 108 within the barrel bore of the weapon
such that sliding friction between the bearing surface portion 110
and barrel bore will be enhanced relative to a comparable bullet of
conventional (i.e., prior art) construction.
[0023] Sliding friction between the bore and the bullet 108 creates
heat in the jacket 120. The lead of the core 118 has relatively low
heat conductivity and the copper alloy of the jacket 120 has
relatively high heat conductivity. Heat produced within the jacket
120 will penetrate the full thickness of the jacket 120 within the
time it takes for the bullet 108 to pass down a length of the
barrel bore of the weapon. When this heat reaches the core 118, the
core 118 serves as an effective insulator thereby causing more heat
to building the jacket 120 and, thus, soften the jacket 120 further
to provide for more sliding friction. Roughly speaking, given
identical frictional heating, a jacket that is three times as thick
as a thinner jacket will heat up about one-third of the amount that
the thinner jacket will heat up. The friction coefficient of copper
is a strong function of the surface hardness and hardness is a
strong function of temperature. In this manner, the jacket 120
being relatively thin further enhances sliding friction between the
bearing surface portion 110 and the barrel bore. In combination
with these frictional and obturation considerations of the bullet
108, the propellant 124 provides gas pressure characteristics
(e.g., peak gas pressure, percent dwell around peak gas pressure,
and average gas pressures) within the barrel bore of the weapon to
generate sufficient gas-pressure derived energy at a gas port of
the weapon for cycling its bolt carrier when the round of
ammunition 100 is discharged. These gas pressure characteristics in
combination with weight of the bullet 108 and frictional forces
exerted on the bullet 108 causes the bullet 108 to decelerate from
a supersonic speed (e.g., at a barrel position where the gas port
is located) to a subsonic speed prior to exiting the barrel
bore.
[0024] It is disclosed herein that the use of a layer of friction
reducing material on the bearing surface portion 110 of the bullet
108 can be used to influence gas pressure characteristics and/or
resulting velocity profile of the bullet 108. For example, as
disclosed above, molybdenum disulfide is one example of a
friction-reducing material composition to which the jacket 120 and
the shot (e.g., steel shot) can be exposed during such shot peening
for causing the exterior surface of the jacket 120 to become coated
with a layer of molybdenum disulfide. Coating the bearing surface
portion 110 with a layer of molybdenum disulfide or other suitable
friction reducing material composition can result in the bullet
exhibiting reduced initial friction in the barrel bore, with
diminishing effect as velocity of the bullet 108 increases (e.g.,
provides negligible effect with suitable velocity). Thus, its
application to the bearing surface portion 110 of the bullet 108
can result in lower initial gas pressure, which moderates and
broadens the initial gas pressure spike produced by combustion of
the propellant 120. In effect, such a layer of friction reducing
material can delay onset of heating of the jacket and thus
influence sliding friction as a function of time.
[0025] It is disclosed herein that configuring a round of
ammunition in accordance with the present invention can include
manipulating ammunition-specific parameters including, but not
limited to, jacket thickness, jacket material composition, jacket
hardness, bearing surface length, core material composition,
propellant type, propellant quantity, and jacket surface coating
presence/type. All or a portion of these ammunition-specific
parameters can be manipulated in view of weapon-specific parameters
including, but not limited to, barrel bore diameter, barrel bore
length, gas port position/size, required bolt actuation mechanism
energy, barrel bore material, etc. In view of the disclosures made
herein, a skilled person will be able to specify
ammunition-specific parameters for ammunition configured in
accordance with the present invention for a particular
configuration of weapon (e.g., a rifle) by experience and/or with
minimal experimentation.
[0026] In the preceding detailed description, reference has been
made to the accompanying drawings that form a part hereof, and in
which are shown by way of illustration specific embodiments in
which the present invention may be practiced. These embodiments,
and certain variants thereof, have been described in sufficient
detail to enable those skilled in the art to practice embodiments
of the present invention. It is to be understood that other
suitable embodiments may be utilized and that logical, mechanical,
chemical and electrical changes may be made without departing from
the spirit or scope of such inventive disclosures. To avoid
unnecessary detail, the description omits certain information known
to those skilled in the art. The preceding detailed description is,
therefore, not intended to be limited to the specific forms set
forth herein, but on the contrary, it is intended to cover such
alternatives, modifications, and equivalents, as can be reasonably
included within the spirit and scope of the appended claims.
* * * * *