U.S. patent application number 09/540569 was filed with the patent office on 2001-12-13 for jacketed frangible bullets.
Invention is credited to Bainer, John R., Davis, George B..
Application Number | 20010050020 09/540569 |
Document ID | / |
Family ID | 26825847 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010050020 |
Kind Code |
A1 |
Davis, George B. ; et
al. |
December 13, 2001 |
Jacketed frangible bullets
Abstract
A frangible bullet for use in training ranges as an alternative
to live ammunition, which disintegrates upon impact with a target.
The frangible bullet includes an elongated frangible core member
fabricated from a thermoplastic polymer and at least one metal, the
core member having a back end, an opposite tip end and a central
portion therebetween, and having a core length between the back end
and the tip end. The core member is jacketed in an outer jacket
having a closed first end and an opposite opened second end, having
a jacket length between the first end and second end, and defining
a jacket chamber for complementarily receiving the core member
therein. The core member fits inside the outer jacket such that the
tip end of the frangible core member is exposed and impacts the
target first, resulting in fragmentation of the core member and the
outer jacket.
Inventors: |
Davis, George B.; (Dumfries,
VA) ; Bainer, John R.; (Dale City, VA) |
Correspondence
Address: |
Needle & Rosenberg PC
Sumner C Rosenberg
The Candler Building Suite 1200
127 Peachtree Street NE
Atlanta
GA
30303-1811
US
|
Family ID: |
26825847 |
Appl. No.: |
09/540569 |
Filed: |
March 31, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60127657 |
Apr 2, 1999 |
|
|
|
Current U.S.
Class: |
102/506 |
Current CPC
Class: |
F42B 12/745
20130101 |
Class at
Publication: |
102/506 |
International
Class: |
F42B 010/00; F42B
012/00; F42B 012/22; F42B 030/00 |
Claims
What I claim is:
1. A frangible bullet, comprising: a. an elongated frangible core
member comprising a thermoplastic polymer and at least one metal,
having a back end, an opposite tip end and a central portion
therebetween, and having a core length between the back end and the
tip end; and b. an outer jacket having a closed first end and an
opposite opened second end, having a jacket length between the
first end and second end, and defining a jacket chamber for
complementarily receiving the core member therein, wherein the back
end of the core member is contained within the outer jacket
adjacent the first end thereof, and wherein the core length is
greater than the jacket length.
2. The frangible bullet of claim 1, wherein the metal of the core
member is in powder form.
3. The frangible bullet of claim 1, wherein the metal of the core
member is in particulate form.
4. The frangible bullet of claim 1, wherein the metal of the core
member comprises a heavy metal.
5. The frangible bullet of claim 4, wherein the core member
comprises two different heavy metals.
6. The frangible bullet of claim 5, wherein the heavy metals are
copper and tungsten.
7. The frangible bullet of claim 4, wherein the metal of the core
member comprises zinc.
8. The frangible bullet of claim 4, wherein the metal of the core
member comprises copper.
9. The frangible bullet of claim 4, wherein the metal of the core
member comprises tungsten.
10. The frangible bullet of claim 4, wherein the metal of the core
member comprises tin.
11. The frangible bullet of claim 1, wherein the outer jacket is
constructed of copper.
12. The frangible bullet of claim 1, wherein the outer jacket
further comprises a jacket exterior surface extending between the
first end and the second end, the exterior surface being coated
with a lubricant.
13. The frangible bullet of claim 1, wherein the thermoplastic
polymer comprises a polyamid.
14. The frangible bullet of claim 1, wherein the thermoplastic
polymer comprises a polyurethane.
15. The frangible bullet of claim 1, wherein the thermoplastic
polymer comprises a polyester.
16. The frangible bullet of claim 13, wherein the polyamid
comprises Type 6 Nylon.
17. The frangible bullet of claim 13, wherein the polyamid
comprises Type 11 Nylon.
18. The frangible bullet of claim 1, wherein the core member
comprises Type 6 Nylon, copper powder and tungsten powder.
19. The frangible bullet of claim 18, wherein the core member has a
specific gravity greater than 5.4.
20. The frangible bullet of claim 18, wherein the core member has a
specific gravity substantially equal to 6.0.
21. A frangible munitions cartridge, comprising: a. a cartridge
case having a base end with a primer disposed therein and an
opposite opened mouth end, the cartridge case defining a chamber
between the two ends and containing a charge therein; b. a
frangible bullet mounted within the opening defined by the mouth
end of the cartridge case, the frangible bullet comprising: an
elongated frangible core member comprising a thermoplastic polymer
and at least one metal, having a back end, an opposite tip end and
a central portion therebetween, and having a core length between
the back end and the tip end; and an outer jacket having a closed
first end and an opposite opened second end, having a jacket length
between the first end and second end, and defining a jacket chamber
for complementarily receiving the core member therein, wherein the
back end of the core member is contained within the outer jacket
adjacent the first end thereof, and wherein the core length is
greater than the jacket length.
22. A method of forming a frangible bullet, comprising: a.
providing an elongated frangible core member comprising a
thermoplastic polymer and at least one metal, having a back end, an
opposite tip end and a central portion therebetween, and having a
core length between the back end and the tip end; b. providing an
outer jacket having a closed first end and an opposite opened
second end, having a jacket length between the first end and second
end, and defining a jacket chamber for complementarily receiving
the core member therein; c. inserting the core member into the
jacket chamber so that the back end of the core member is adjacent
the first end of the outer jacket; and d. crimping the outer jacket
adjacent the second end to fixedly secure the core member within
the outer jacket.
Description
RELATED U.S. APPLICATION DATA
[0001] This application claims priority to U.S. provisional
application Ser. No. 60/127,657 filed on Apr. 2, 1999. The No.
60/127,657 provisional patent application is herein incorporated by
this reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to frangible ammunition or
bullets for use in training ranges as an alternative to live
ammunition. More specifically, the invention relates to frangible
bullets having a heavy metal loaded polymer core which is partially
jacketed in a high-density high-strength material, such as
copper.
[0004] 2. Background Art
[0005] Traditionally, rifle bullets have been manufactured from
lead. Lead has been a preferred material mainly because of its high
density, which is beneficial for range of firing and for weapon
functioning. Furthermore, because of their high ductility, lead
bullets may be easily manufactured in various shapes and sizes.
While lead has many characteristics beneficial to bullet
manufacture, it also has drawbacks. Lead is a toxic metal that
presents a health risk to the shooter from lead fumes and dust, and
endangers the environment through contamination of ground water
supplies.
[0006] In addition to the health and environmental issues addressed
above, lead rifle bullets present additional hazards to individuals
engaged in weapons training and to the range infrastructure, such
as over-penetration, ricochet and backsplatter. Lead rifle bullets,
particularly those used in the military, are designed to penetrate
hard surfaces such as mild steel and concrete. While in a combat
situation this penetration may be desirable, in training it causes
costly damage to target systems and training structures.
[0007] These environmental, health, and bullet performance concerns
have precipitated a number of bullet developments and innovations.
New bullet designs have emerged which incorporate a variety of
non-toxic material alternatives to the lead contained in standard
ammunition. Included in this group are a number bullet designs
utilizing heavy metal loaded polymers, generally classified as
"frangible" ammunition.
[0008] Frangible bullets, which typically contain no lead, were
designed to address both the physical hazards and adverse
performance characteristics of lead bullets. The heavy metal loaded
polymer construction of these bullets was designed to ensure
consistent breakup of the bullet on impact with solid materials
such as steel. These early frangible rifle bullets demonstrated a
significant reduction in ricochet with a total elimination of lead
toxins.
[0009] FIG. 1 shows a prior art unjacketed, one piece, polymer
frangible bullet. The bullet has a cylindrical body formed with a
tapered nose portion. Prior art bullets of this type are commonly
manufactured by injection molding. A common composition of such
prior art frangible bullets is a compounded mixture of type 11
nylon (known generally in the art as N11 nylon), copper powder and
tungsten powder. A typical bullet manufactured of such a mixture in
the shape depicted in FIG. 1 weighs 33 grains.
[0010] There are a number of competing design considerations at
work in the construction of a frangible bullet. A primary design
focus for developers of this type of bullet has always been bullet
weight. Prior art bullets have been molded from a compound
comprising a metal powder or combination of metal powders combined
with a nylon polymer. The metal powder mixture is incorporated with
the nylon polymer to provide an increased bullet weight over bullet
constructions containing only nylon polymer. Of course, an
increased density or ratio of metal powder to nylon in the bullet
composition produces a commensurate increase in bullet weight.
Bullet weights that approximate the weight of standard lead-core
bullets are most conducive to proper weapon functioning. Bullet
weights that approach the weight of standard bullets also improve
bullet down-range accuracy by sustaining higher bullet energy
levels at greater distances.
[0011] Reliable weapons functioning in most automatic and
semiautomatic rifles is a result of adequate gas pressure, produced
by the burning propellant in the cartridge, reaching the rifle's
gas operating system. Higher gas pressure within the barrel
frequently has a direct, positive effect on the reliability of
weapon. Bullet weight is also relevant to reliability of weapons
functioning. The cartridge, regardless of the bullet weight,
produces approximately the same initial gas pressure within the
barrel. The amount and type of powder utilized, not the bullet
composition, dictates the initial pressure level. As the powder
burns, pressure builds behind the bullet, causing the bullet to
travel down the barrel of the weapon toward the gas port located
near the muzzle. The pressure level rearward of the bullet as the
bullet passes the gas port is critical to proper weapon
functioning.
[0012] The heavier the bullet, the greater its inertia, and
consequently the slower its initial velocity within the barrel. A
heavier, slower moving bullet provides more time for the powder to
burn, resulting in a higher pressure buildup within the barrel, and
particularly at the gas port. Inversely, lighter bullets travel
through the barrel at increased velocities, resulting in reduced
pressure at the gas port.
[0013] One solution is to increase the ratio of metal powders to
polymer until the desired bullet weight is obtained. However, the
physical dimensional constraints of the bullet limit the overall
bullet weight using existing metal powders and polymer materials.
The physical dimensions of the rifle chamber fix the bullet's
diameter and overall length. Therefore, all combinations of metal
powders and polymer are constrained in overall volume by the
requirement of dimensional compatibility with existing
weaponry.
[0014] Other elements constraining the ratio of metal powders to
polymer are the desired terminal characteristics of the bullet and
the internal ballistic environment within the chamber of the
weapon. The desired terminal effect of a frangible bullet is
frangibility. It is desired that the bullet disintegrate as
completely as possible upon impact with solid objects. Total
disintegration to dust is the ultimate design objective. The degree
of fragmentation is determined in part by bullet diameter and
terminal velocity. Generally, the smaller the bullet diameter and
higher the terminal velocity, the more complete the disintegration.
In the case of heavy metal loaded polymer frangible bullets, the
fragmentation or disintegration of the bullet on impact is also a
function of the ratio of metals to polymer. The polymer dictates
the strength of the bullet. Thus, a higher relative content of
polymer produces a stronger bullet. While this consideration would
appear to further support the use of higher ratios of metals in
frangible bullet design, the ratio is constrained by the internal
ballistic environment that the bullet must survive within the
weapon.
[0015] Internal chamber pressures of automatic and semiautomatic
rifles are approximately 50,000 pounds per square inch, and bullet
velocities exceed 3,000 feet per second. The material strength of
polymer frangible bullets must be sufficient to withstand these
extreme pressures and velocities. If the ratio of metal to polymer
is too high, the bullet will suffer a catastrophic, in-bore
failure, which may damage the weapon and present a physical hazard
to people in the proximity of the weapon. Thus, to ensure
sufficient bullet strength, a minimum polymer to metals ratio must
be maintained in the compound.
[0016] In addition to high chamber pressures and supersonic
velocities, polymer bullets must also endure high chamber and
barrel temperatures that result from automatic fire. These
temperatures may exceed the melting temperature of the polymer used
in the bullet's compound. Thus, if the bullet remains in the
chamber too long before exiting, the polymer may soften, again
resulting in a catastrophic bullet failure. This is especially the
case in prior art unjacketed frangible bullet designs, in which the
bullet material is exposed directly to the combustion gases which
propel the bullet through the barrel.
[0017] In 1997, the Light Weapons Division of the Armament and
Ammunition Testing Directorate of the U.S. Army Aberdeen Test
Center, Aberdeen Proving Grounds, Md., published a Report of a
Technical Feasibility Test of then-existing 5.56 mm and 9 mm
Frangible Training Ammunition. This early government testing of
unjacketed polymer ammunition documented unacceptable operational
reliability for frangible rifle caliber bullets as a direct result
of low chamber/gas port pressures across the spectrum of material
candidates. In addition, all candidate bullets tested performed
poorly in accuracy testing at ranges exceeding 50 meters. Some
candidate compounds also suffered catastrophic failure due to
inadequate bullet strength.
[0018] Thus, it is an object of the invention to provide a
non-toxic frangible bullet which will provide the necessary bullet
weight to function reliably in existing firearms. More
specifically, significant demand exists for a such a frangible
bullet for use in military automatic rifles and light machine
guns.
[0019] It is a further object of the invention to eliminate the
potential of catastrophic bullet failure by ensuring material
strength and core isolation from chamber heat.
[0020] It is a further object of the invention to improve the
accuracy and performance of polymer frangible bullets by increasing
both bullet weight and bullet to barrel interface.
[0021] It is a further object of the invention to accomplish the
above-mentioned improvements without sacrificing the reduced
over-penetration, ricochet and backsplatter hazard characteristics
previously demonstrated by unjacketed polymer frangible
bullets.
SUMMARY OF THE INVENTION
[0022] The disadvantages of the prior art are overcome by the
present invention which, in one aspect, is a frangible bullet
having a core member constructed of a mixture containing a
thermoplastic polymer and a lead-free heavy metal, in combination
with an outer jacket. The core member has a back end, an opposite
tip end, and a central portion therebetween, defining a core length
between the back end and the tip end. In one embodiment, a core
member having suitable strength and weight characteristics may be
formed from a mixture of a type 6 nylon polymer, copper powder, and
tungsten powder.
[0023] The outer jacket, which may be constructed of copper or
other suitable high density, high strength metal, plastic or other
polymer, has an enclosed first end and an opposite open second end
defining a jacket length between its two ends. The outer jacket
defines a jacket chamber for encapsulating the back end and a part
of the central portion of the core member, thereby shielding the
core member from the high chamber temperatures which have led to
in-bore bullet failure in prior art frangible bullet embodiments.
The outer jacket also forms the circumferential perimeter of the
bullet of the present invention, enabling more precise control of
bullet caliber than is possible in prior art designs.
[0024] The outer jacket is configured such that the nose or tip of
the frangible core member is exposed. Thus, the unjacketed tip end
of the core member impacts the target first. Deceleration shock on
impact causes disintegration of the bullet core member, and
rearward radiation of that shock ensures fragmentation of the outer
jacket.
[0025] Addition of the outer jacket to the frangible core member
increases the bullet's dynamic strength such that less costly,
lower shear strength polymer materials may be utilized in
manufacture of the core member. In addition to an increased
cost-effectiveness, use of a lower shear strength polymer also
ensures more complete disintegration of the core member upon bullet
impact. Incorporation of the outer jacket into the bullet design
also results in an increased bullet weight, which yields greater
reliability and accuracy than may be obtained with prior art
unjacketed frangible ammunition.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS
[0026] FIG. 1 is a side elevational view of a prior art unjacketed
frangible bullet.
[0027] FIG. 2 is a perspective view of a frangible munitions
cartridge according to the present invention.
[0028] FIG. 3 is a side elevational view of an embodiment of the
core member of the jacketed frangible bullet according to the
present invention.
[0029] FIG. 4 is a side elevational view of an embodiment of the
jacketed frangible bullet according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The present invention is more particularly described in the
following examples that are intended as illustrative only since
numerous modifications and variations therein will be apparent to
those skilled in the art. As used in the specification and in the
claims, "a" can mean one or more, depending upon the context in
which it is used. The preferred embodiment is now described with
reference to the figures, in which like components indicate like
parts throughout the figures.
[0031] As shown in FIGS. 2 and 4, in one embodiment, the invention
is a jacketed frangible bullet 20 having two main components, an
elongated frangible core member 30 and an outer jacket 40. The
embodiment pictured in FIGS. 2 and 4 represents a 5.56 mm jacketed
frangible bullet 20 designed for rifle use, but it should be
understood that the scope of this invention extends to all calibers
of bullets for use in any pistol or manual, semi-automatic or
fully-automatic rifle or machine gun, or any other weapon system in
which use of a frangible bullet 20 is advantageous.
[0032] Referring to FIG. 3, the core member 30 has a back end 32,
an opposite tip end 34 and a central portion 36 therebetween. The
length of the core member 30, or the core length L1, is defined by
the distance between the back end 32 and the tip end 34. In the
embodiment illustrated in FIGS. 3 and 4, corresponding to a 5.56 mm
rifle bullet, the core length L1 is approximately 0.8 inch.
[0033] The core member 30 is fabricated from materials including a
thermoplastic polymer and at least one metal. Both type 11 and type
6 nylon materials (commonly known in the art as N11 and N6 nylons,
respectively), have been successfully utilized in fabricating
frangible munitions. It has been discovered that N6 nylon is
preferable to N11 nylon because of its lower cost and higher
specific gravity and because of its greater frangibility. N11
nylon, however, exhibits greater shear strength and bonding
characteristics over N6 nylon, such that use of N11 nylon permits
the use of an increased ratio of metal powder to thermoplastic
polymer in the core member 30 composition.
[0034] In prior art unjacketed frangible bullet designs for 5.56 mm
weapons, as shown in FIG. 1, bullet performance criteria have not
been met by bullets utilizing the less expensive N6 nylon material.
Thus, prior art 5.56 mm unjacketed frangible bullets have been
manufactured using N11 nylon materials. As discussed in detail
below, however, by the addition of an outer jacket 40 to the
frangible bullet 20, dynamic strength characteristics of the bullet
20 are significantly improved, permitting the use of the less
costly and lower shear strength N6 nylon material as the bonding
agent for the compound. Use of the N6 nylon results in a core
material more frangible than compound made with the N11 nylon.
[0035] According to the invention, other thermoplastic polymer
materials in addition to those discussed above may also be
utilized, including other polyamids (including other nylon
formulations), polyesters and polyurethanes. Additionally, the
thermoplastic polymer component may be fabricated partially or
exclusively of polyvinyl chloride, fluorocarbons, linear
polyethylene, polyurethane prepolymer, polystyrene, polypropylene
and cellulosic and acrylic resins. It is critical, however, that
the selected thermoplastic polymer utilized to form the core member
30 be highly frangible in order not to increase the terminal
penetration effects of the bullet 20.
[0036] A metal component is provided in combination with the
above-described thermoplastic polymer to form the core member 30.
The metal component of the core member 30 includes at least one
metal, and may include a combination of two or more metals as
needed to achieve the desired bullet weight for the selected weapon
system. Metal components are selected, in part, based upon their
density and their suitability for combination with the selected
thermoplastic polymer to form a completed core member 30. Because
of their relatively high specific gravity, heavy metal elements
have been utilized to form the metal component of the core member
30.
[0037] The metal component is commonly utilized in powder form,
because of the relative ease with which powdered metals may be
mixed and combined with the thermoplastic polymer material.
Alternatively, metals in particulate or other forms may be utilized
if they are capable of combination with the thermoplastic
polymer.
[0038] In one embodiment, copper powder and tungsten powder are
have been utilized to form the metal component of the core member
30. In a currently preferred embodiment, a core member 30 including
N6 nylon, copper powder and tungsten powder is utilized, in
relative concentrations that result in an overall core member 30
specific gravity of 6.0. This material is commercially available
from Saracen Chemicals, Ltd., a United Kingdom company with offices
at Vulcan House, Restmer Way, Hackbridge, Surrey, SM6 7AH, England.
This material has been found to exhibit superior frangibility over
a similar material containing N11 nylon, copper powder and tungsten
powder having a specific gravity of 5.4. The addition of the outer
jacket 40, which significantly increases the structural and thermal
durability of the bullet 20, enables use of the N6 nylon core
member 30, resulting in reduced cost and superior performance over
the prior art.
[0039] Other metals may be utilized in the core member 30 without
departing from the scope of the invention. Selected or combined
heavy metals including transition metals, lanthanides and actinides
provide suitable mass to the core member 30 to meet performance
criteria of frangible ammunition. Because of price, availability
and manufacturing concerns, four common metals have been primarily
utilized in the art: zinc, tin, copper and tungsten. Any metal
selected from this group may be utilized to produce frangible
ammunition according to the invention.
[0040] Once the constituent materials are selected, the core member
30 may be manufactured according to methods known in the art,
including injection molding.
[0041] FIG. 3 illustrates a reduced diameter, 30-grain frangible
bullet core member 30 according to the present invention,
compounded of a mixture of N6 nylon, copper powder and tungsten
powder. The core diameter is reduced relative to unjacketed bullet
core members to allow for application of the outer jacket 40
illustrated in FIGS. 2 and 4 and as described in detail below.
[0042] FIGS. 2 and 4 illustrate the placement of the outer jacket
40 on the frangible core member 30. Encapsulating the core member
30 in the outer jacket 40 isolates the core member 30 from direct
contact with the heated chamber of the weapon, significantly
reducing the potential for softening of the material and in-bore
catastrophic failure of the bullet 20.
[0043] The outer jacket 40 has a closed first end 42 and an
opposite opened second end 44. The jacket length L2 is the distance
between the first end 42 and the second end 44 of the outer jacket
40. The hollow interior of the outer jacket 40 is referred to
herein as the jacket chamber. The outer jacket 40 encloses a
portion of the frangible core member 30, including the back end 32
and a portion of the central portion 36 of the core member 30,
leaving at least the tip end 34 fully exposed. Installation of the
outer jacket 40 over the back end 32 of the core member 30 with the
tip end 34 exposed ensures that the frangible material will impact
the target first. The deceleration shock generated by impact
radiates rearward, ensuring the effective disintegration of the
entire core member 30.
[0044] Outer jackets 40 fabricated from copper have been utilized
and found acceptable for use in the present invention because of
the ductility, weight and deformability of copper. Other materials
may be utilized to form the outer jacket 40 without departing from
the scope of the invention. For example, outer jackets 40 may be
fabricated from other metals, including mild steel, guilding metal,
guilding clad steel or coated tin. Alternatively, synthetic
thermoplastic polymer materials may be utilized to form the outer
jacket 40, provided that the selected polymer exhibits sufficient
rigidity under barrel operating temperatures, without departing
from the invention.
[0045] When assembled, the back end 32 of the core member 30 is
inserted into the jacket chamber until the back end 32 is seated
adjacent the first end 42 of the outer jacket 40. Using a dial
press, a hand press or other methods known in the art, the second
end 44 of the outer jacket 40 is crimped or necked-down to fixedly
secure the core member 30 within the outer jacket 40. Adding this
outer jacket 40 to the 30-grain core member 30 produces an overall
bullet weight of 45 grains. This jacketing procedure increases the
5.56 mm bullet weight by 36 percent.
[0046] In the illustrated embodiment, the dimensions of the core
member 30 and the outer jacket 40 are controlled such that the core
length L1 is greater than the jacket length L2. Consequently, the
tip end 34, or ogive, of the core member 30 is unjacketed and
exposed to impact with targets. As discussed above, this condition
has been found to promote full frangibility without significantly
compromising performance of the munitions. Conversely, testing
conducted with fully copper-jacketed frangible bullets has resulted
in over penetration and significantly limited disintegration of the
bullet.
[0047] Additionally, a lubricant may be applied to the exterior
surface of the outer jacket 40 to improve weapon performance.
Suitable lubricants include coatings such as Teflon, a variety of
oil-based lubricants such as Militec, and a variety of powder-based
lubricants such as graphite, which are known generally in the art.
It should be noted that the use of some lubricants such as Teflon
is restricted by various legislation currently in place.
[0048] An operational frangible munitions cartridge 50 is produced
by loading the frangible bullet 20 described above into a cartridge
case 52. Referring now to FIG. 2, the cartridge case 52 has a base
end 54 and an opposite opened mouth end 56. The cartridge case 52
is generally hollow, defining a chamber therein which is loaded
with powder and air to provide a charge.
[0049] The jacketed frangible bullet 20 is mounted within the
opening defined by the mouth end 56 of the cartridge case 52 as is
generally known in the art. The jacketed frangible bullet 20
protrudes from the mouth end 56 of the cartridge case 52, such that
the first end 42 and a portion of the outer jacket 40 are contained
within the cartridge case 52. The second end 44 of the outer jacket
40 and the remaining portion of the outer jacket 40, including the
crimped or necked-down portion of the outer jacket 40 and the tip
end 34 of the core member 30, protrude from the mouth end 56 of the
cartridge case 52.
[0050] A primer (not shown) is provided in the base end 54 of the
cartridge case 52 that detonates the charge when the weapon is
fired. The sudden and substantial pressure created by the
combustion of the charge within the confined chamber within the
cartridge case 52 impart the forces necessary to eject the
frangible bullet 20 from the cartridge case 52 and accelerate the
bullet 20 to its firing speed.
[0051] The diameter of the bullet 20 illustrated in FIG. 4 is full
caliber, meaning that the outside dimension of the bullet 20
conforms to the minimum and maximum outside dimensions established
for this caliber bullet 20 by the Sporting Arms and Ammunition
Manufacturers Institute (SAAMI) specification. The overall length
of the cartridge 50, once loaded in the cartridge case 52, also
falls within those standards.
[0052] Testing Results
[0053] Testing of an unjacketed 33-grain 5.56 mm frangible
cartridge described above in the discussion of the prior art
provided pressure results at the chamber of 124,136 pounds per
square inch and 9,695 pounds per square inch at the gas port. These
results indicate that the unjacketed 33-grain bullet of the prior
art was producing case pressures 8,000 to 10,000 pounds per square
inch less than currently used, non-frangible military ball
ammunition. More importantly, the gas port pressures for the prior
art style frangible bullet were 3,000 pounds per square inch lower
than the minimal acceptable value for ball ammunition. The
government's Report of its Technical Feasibility Test concluded
that "[t]he ramification of these differences is that weapon
function may be degraded across the temperature profile since all
5.56 mm weapon systems are gas operated."
[0054] In contrast to test results from prior art unjacketed
33-grain bullet test results, testing of the heavier, copper
jacketed 45-grain 5.56 mm bullet according to one embodiment of the
present invention demonstrated not only improvement, but pressures
and accuracy equal to or surpassing that achieved by conventional
military combat ball ammunition. In side-by-side testing, the new
45-grain bullet produced chamber pressures and gas port pressures
of 50,300 and 14,915 pounds per square inch respectively, while the
military's issued ammunition provided pressures of 47,000 and
15,139 pounds per square inch. These improved pressures result in
enhanced reliability and performance of the frangible cartridge to
levels that satisfy the military's requirement.
[0055] In addition, accuracy improvements surpassed the performance
of military ball ammunition at 100 meters and matched military
ball's performance at 200 meters. Equally important, side-by-side
comparative testing of the 33-grain unjacketed bullet and the
45-grain jacketed bullet demonstrated no measurable penetration or
frangibility difference between the two cartridges.
[0056] During all testing by both the inventors and by the
government, no instance of catastrophic failure of the jacketed
45-grain bullet was experienced at operating temperatures that
ranged from 60 to -29 degrees C.
[0057] Although the present invention has been described with
reference to specific details of certain embodiments thereof, it is
not intended that such details should be regarded as limitations
upon the scope of the invention except as and to the extent that
they are included in the accompanying claims.
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