U.S. patent application number 09/952849 was filed with the patent office on 2002-01-17 for lead-free frangible projectile.
Invention is credited to Stone, Jeffrey W..
Application Number | 20020005137 09/952849 |
Document ID | / |
Family ID | 21748665 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020005137 |
Kind Code |
A1 |
Stone, Jeffrey W. |
January 17, 2002 |
Lead-free frangible projectile
Abstract
Frangible projectiles free of heavy metals suitable for use in
indoor target ranges comprising tungsten and at least one metal
selected from the group consisting of iron and copper. The
projectiles are prepared from a mixture of tungsten and iron
powders, tungsten and copper powders, or tungsten, iron and copper
powders and compacted without sintering.
Inventors: |
Stone, Jeffrey W.;
(Elizabethtown, KY) |
Correspondence
Address: |
Huntley & Associates
1105 N. Market Street
P.O. Box 948
Wilmington
DE
19899-0948
US
|
Family ID: |
21748665 |
Appl. No.: |
09/952849 |
Filed: |
September 14, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09952849 |
Sep 14, 2001 |
|
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08755963 |
Nov 25, 1996 |
|
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|
60011053 |
Jan 25, 1996 |
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Current U.S.
Class: |
102/517 |
Current CPC
Class: |
F42B 12/74 20130101;
F42B 8/16 20130101 |
Class at
Publication: |
102/517 |
International
Class: |
F42B 010/00; F42B
012/00; F42B 030/00 |
Claims
I claim:
1. A lead free projectile comprising a compacted, unsintered
admixture of metal particles comprising, by weight, about from 20
to 59% tungsten about from 40 to 80% copper and about from 1 to 15%
iron, and wherein the particle size of each metal is about from 25
to 250 microns.
2. A projectile of claim 1 wherein the composition by weight of
each metal in the admixture is about 29% tungsten, 66% copper, and
5% iron.
3. A projectile of claim 1 wherein the particle size of each metal
is at least about 100 microns.
4. A projectile of claim 1 wherein the particle size of each metal
is at least about 150 microns.
5. A projectile of claim 1 further comprising an outer jacket.
6. A projectile of claim 5 wherein the outer jacket consists
essentially of metal.
7. A projectile of claim 6 wherein the metal is selected from the
group consisting of copper, aluminum, and zinc.
8. A projectile of claim 7 wherein the outer jacket consists
essentially of copper.
9. A projectile of claim 5 wherein the outer jacket consists
essentially of polymeric material.
10. A projectile of claim 9 wherein the polymeric material is
thermoplastic.
11. A projectile of claim 10 wherein the thermoplastic is selected
from the group consisting of polyethylene, polyamide,
polycarbonate, and polystyrene.
12. A projectile of claim 9 wherein the polymeric material is a
thermosetting resin.
13. A projectile of claim 12 wherein the thermosetting resin is
selected from the group consisting of phenolic, epoxy, and silicone
resins.
14. A projectile of claim 11 wherein the outer jacket consists
essentially of polyethylene.
15. A projectile of claim 1 in a bullet configuration.
16. A projectile of claim 1 in a shot configuration.
17. A projectile of claim 1 in a slug configuration.
18. A process for the preparation of a lead free projectile
comprising placing in a die a powdered admixture of tungsten and at
least one metal selected from the group consisting of iron and
copper, wherein the particle size of each metal is about from 25 to
250 microns, and compacting the admixture at a pressure of about
from 50,000 to 120,000 psi.
19. A process of claim 18 wherein the admixture is compacted at a
pressure of about 100,000 psi.
20. A process of claim 18 further comprising applying a jacketing
material to the resulting projectile.
21. A process of claim 20 wherein the jacketing material is
polymeric.
22. A process of claim 21 wherein the polymeric jacketing material
is selected from the group consisting of polyethylene, polyamide,
polycarbonate, or polystyrene.
23. A process of claim 20 wherein the jacketing material is
metal.
24. A process of claim 23 wherein the jacketing material is
selected from the group consisting of copper, aluminum, and
zinc.
25. A process of claim 23 wherein the jacketing material is formed
around the projectile.
26. A process of claim 23 wherein the jacketing material is plated
onto the projectile.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of application Ser. No.
08/755,963, which is based on Provisional Application No.
60/011,053.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to ammunition and more
particularly to frangible target ammunition, training ammunition,
or sporting ammunition.
[0003] A need exists for training ammunition that can be used in
indoor target ranges. Such ammunition must be frangible to reduce
or eliminate the potential for ricochet. A frangible bullet, upon
impact with its target, will disintegrate with no appreciable back
splatter or ricochet as to cause bodily injury to the shooter or
others. The need for frangible ammunition has previously been
satisfied by bullets made substantially of lead.
[0004] Lead bullets, while providing the desired frangibility, also
produce unwanted health risks. When fired, a lead bullet introduces
airborne and residual lead particles into the air, thereby posing a
threat to the health of those in the range, including employees of
the range. Additionally, the lead particles produced when the
bullet disintegrates upon impact with the target pose an
environmental problem. The lead particles are expensive to remove,
and costly to dispose of due to their toxicity. The natural
toxicity of lead has prompted the search for satisfactory
substitutes in a wide variety of applications.
SUMMARY OF THE INVENTION
[0005] The projectiles of the present invention satisfy the need
for frangible lead free projectiles. The projectiles of the present
invention closely mimic the performance and ballistic properties of
lead projectiles without the negative health and environmental
properties associated with lead and other heavy metal
projectiles.
[0006] Specifically, the present invention provides lead free
projectiles consisting essentially of a compacted, unsintered
admixture of metal particles comprising tungsten and at least one
metal selected from the group consisting of iron and copper,
wherein the admixture is about from 10 to 90% by weight tungsten;
wherein the particle size of each metal is about from 25 to 250
microns.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The present invention will be more fully understood by
reference to the following description. Both a process for the
preparation of frangible lead free projectiles and the lead free
projectiles themselves are described below. Variations and
modifications of both the process and the disclosed embodiments of
the projectiles can be substituted without departing from the
principles of the invention, as will be evident to those skilled in
the art.
[0008] The lead free projectiles of the present invention consist
essentially of compacted, unsintered admixture of metal particles
comprising tungsten and at least one metal selected from the group
consisting of iron and copper. The amount by weight of tungsten in
the admixture is about from 10 to 90%, and preferably about from 20
to 70%. The particle size of each metal is about from 25 to 250
microns, and preferably at least about 100 microns.
[0009] The particle size of the metal particles can be determined
by a variety of methods, including conventional optical measurement
and sifting. A particle size of at least about 150 microns is
particularly preferred. Larger particle sizes have been found to
provide a desirable balance between integrity of the projectiles
before and during firing, and frangibility upon impact with a
target. While the relationship between particle size and
performance is not fully understood, it is believed to be a
function of the mechanical interlocking of the particles in the
compressed, but unsintered, projectiles. This effect is generally
more pronounced in larger particles.
[0010] The metals used in combination with tungsten are available
in the designated particle size, or can be ground to the size
required. The copper can be used in its elemental form or as an
alloy such as copper 220 or 260.
[0011] The projectiles of the present invention include a variety
of small arms projectiles such as centerfire ammunition from 0.17
to 0.50 caliber, shot pellets from #9 through 00 buck sizes,
shotgun slugs from 0.410 bore to 12 guage, and rimfire ammunition
in 0.22 caliber.
[0012] The projectiles of the invention can further comprise an
outer jacket. In one possible embodiment the jacket consists
essentially of metal. A wide variety of metals can be used, but the
metal is preferably selected from the group consisting of copper,
brass, aluminum, and zinc. Copper is particularly preferred. In
another embodiment of the invention, the jacket consists
essentially of polymeric material. A wide variety of polymeric
materials can be used including semi-crystalline or amorphous
thermoplastics, or thermosetting resins. Representative
thermoplastic polymers which can be used include polyethylenes,
polyamides, polycarbonates, and polystyrenes. Representative
thermosetting resins which can be used include phenolics, epoxys,
and silicones. Of the above polymeric materials, polyethylene is
particularly preferred.
[0013] The nose of the centerfire and/or rimfire bullets of the
present invention can be configured in a wide variety of profiles,
including round nose, soft nose, or hollow point. In addition, the
projectiles of the present invention can have a full metal jacket.
When the projectiles are in the configuration of a bullet, they can
include a driving band, or in embodiments with a jacket, the jacket
can comprise a driving band. The driving band increases bullet
accuracy and reduces bullet dispersion. The driving band also
reduces friction between projectile and barrel, thereby increasing
velocity without appreciable pressure increase. Shot pellets of the
present invention can be spherical or have an eccentricity which
improves or tightens shot dispersion. The shot pellets can
optionally be plated by electrochemical methods with metal to
increase lubricity and reduce corrosion. The preferred metal is
copper. The shot pellets can also be coated with a polymeric
material as mentioned above, preferably polyethylene or other
linear low density polymeric material. Shotgun slugs will have
either a forward biased centroid for pressure stabilization or a
rearward biased centroid for spin stabilization. The slugs may
utilize a sabot or polymeric coating mentioned above. Preferred
polymeric coatings are polyethylene or other low density
materials.
[0014] The frangible, lead free projectiles of the present
invention can be prepared by a process where in an admixture of
tungsten and at least one metal selected from the group consisting
of iron and copper is placed in a feeder or hopper. The feeder or
hopper dispenses a metered amount into die cavities of a rotary
dial press. The material is compacted either in a single compaction
step or in multiple compaction stages with a pressure of about from
50,000 to 120,000 psi. Compacting the admixture at a pressure of
about 100,000 psi is preferred. The resultant effective density is
in the range of about from 7.0 to 10.5 g/cc.
[0015] The range compaction die should be of a near net shape to
the final projectile. For centerfire, rimfire, and rearward biased
centroid slugs, the preferred compaction force is applied to the
base or rear of the projectile. As a result of the compacting
process, the resulting bullet is formed with a higher density
toward its tail or rear end, and a lower density at its nose or
tip. This measured rearward density promotes greater gyroscopic and
dynamic stability, thus reducing bullet dispersion, increasing
frangibility, and increasing accuracy. For forward biased centroid
slugs, the compaction force is applied at the nose of the
projectile. For shot pellets it is preferred that the compaction
forces be applied equally to both hemispheres of the projectile, to
ensure the projectile centroid is located at the geometric center
of the projectile.
[0016] The desired cycle time of the powder compaction and
subsequent projectile core formation is from 300 to 600 pints per
minute. The finished cores are preferably slightly undersized to
allow for the additions of jackets, plates, coatings, etc. The
projectile coatings, jackets, or plates can be applied, for
example, electrochemical, aerosol, or mechanical methods. The
jacketing material to be applied can be metallic or polymeric as
noted above. The jacketing material can be formed around the lead
free projectile, or in the alternative, the jacketing material can
be plated into the lead free bullet. As a final finishing
operation, the projectiles can be swaged in a hydraulic press to
add uniformity of appearance and exterior dimension.
[0017] The present invention provides lead free frangible
projectiles from an improved composition of metals, the projectiles
having a desirable combination of advantages. Specifically, the
present invention provides projectiles that mimic the firing
characteristics, performance, and frangibility of lead bullets
without the negative health and environmental qualities associated
with lead. The present invention minimizes the threat to human
health associated with direct or indirect contact to airborne or
residual lead particles by providing lead free projectiles.
Similarly, by eliminating lead, the cleanup and disposal of the
fragments of the projectiles of the present invention is safer,
less expensive, and the resulting waste is not highly toxic and
does not require special disposal.
[0018] While reducing the health and environmental problems
associated with lead or other heavy metal projectiles, the bullets
of the present invention mimic the desirable properties associated
with lead projectiles. When fired they produce a recoil which is
perceived by the shooter to be less than or similar to that
produced lead projectiles. The lead free bullets of the present
invention also mimic the ballistic performance of lead bullets so
that their respective point of impact, accuracy, and trajectory
closely approximate lead projectiles. The weight of a projectile of
the present invention also closely approximates the weight of a
lead projectile of the same size and caliber. The projectiles of
the present invention are also frangible, and upon impact with a
target, disintegrate without appreciable back splatter or
ricochet.
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