Note: Descriptions are shown in the official language in which they were submitted.
CA 02432820 2003-06-19
COMPOSITION FOR PRODUCTION OF NON-TOXIC PROJECTILES AND METHOD
OF MANUFACTURING THEREOF
FIELD OF THE INVENTION
The present invention relates to non-toxic projectiles, particularly non-toxic
shot, bullet cores
and solid bullets, and methods of manufacture thereof. The present invention
also relates to
a metal-rubber composition for manufacturing non-toxic projectiles.
BACKGROUND OF THE INVENTION
Traditionally, ammunition for hunting has been manufactured using lead or lead
alloys due
to the high density, malleability and low melting points of these materials.
However, the
toxicity of lead has resulted in recent government restrictions against using
lead shot for
hunting, and particularly for hunting waterfowl.
The use of lead shot-filled shotgun shells for hunting, typically for ducks
and geese, results
in the release of thousands of tonnes of lead into the environment each year.
The lead shot
builds up in the bottom sediments of lakes and wetlands, and breaks down,
transferring lead
into the environment and contaminating source water. Additionally, lead shot
is frequently
ingested by birds causing lead toxicosis.
UVaterfowl most often die from ingesting lead shot, and due to its widespread
use, from
northern breeding grounds to southern wintering grounds, it is available to
waterfiowl feeding
in hunting areas from fall through spring. As a result, mortality accrues
throughout most of
the year, although the majority of lead toxicosis mortalities occur after the
hunting season -
in winter and early spring.
The full impact of lead toxicosis on waterfowl populations has been difficult
to determine,
since predators quickly dispose of moribund birds. Also, poisoned birds
frequently hide
themselves and die in out-of -the way places where they are never found.
However, it is
estimated that thousands of migrating waterfowl die from lead poisoning every
year, and
many others suffer from a milder form of the disease.
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CA 02432820 2003-06-19
In order to reduce the impact of lead on the environment, and to preserve the
waterfowl
population, many governments have restricted the use of lead shot and
k~ullets. In particular,
a nationwide ban on the use of lead shot for hunting waterfowl was implemented
in the
United States in 1991. More recently, Canada implemented a set of regulations
requiring the
use of non-toxic shot in all areas of Canada for hunting most migratory game
birds (including
ducks, geese, brant, cranes, rails, gallinules, coots, and snipe) by September
1, 1999.
Canada and the United States have approved several types of non-toxic shot,
including steel,
bismuth, tungsten-iron, tungsten-polymer, tungsten-matrix and tungsten-nickel-
iron. Canada
also allows use of tin, although tin shot is no longer approved for hunting
waterfowl in the
United States.
Steel shot is the most common and affordable of the non-toxic shot options.
However, steel
does not share the same physical and ballistic characteristics as lead. Steel
is much harder,
meaning there is a potential risk that older shotgun barrels may be damaged
when firing steel
shot. Also, steel shot does not deform during flight, and tends to penetrate
completely
through the target. This results in an increased incidence of wounding rather
than humane
killing. In contrast, lead shot flattens due to lead's high degree of
malleability, thus providing
a higher surface area for impact. This results in a higher amount of energy to
be transferred
directly to the target, thereby providing a more humane kill. Steel is also
relatively lightweight,
meaning that to attain similar energy levels as lead, a hunter must switch to
a larger steel
shot size. Steel shot also loses energy more quickly than lead, reducing the
ranges at which
it is most effective.
Bismuth, on the other hand, is roughly 85 per cent as dense as lead, resulting
in somewhat
similar ballistic properties. Bismuth shot sizes appropriate for a given
hunting situation are
similar to those of lead, and effective shooting ranges are virtually
identical. However,
bismuth is less abundant than lead and steel, and therefore more costly.
Additionally, tests
of the Bismuth Cartridge Company's No-ToxT"" shot found this type of shot to
be too fragile
("Steel 3-inch Magnum Loads Our Pick For Waterfowl Hunting", January 1998
issue of Gun
Tests). This is not surprising, since bismuth alloys used for manufacturing
this type of shot
are inherently brittle.
Tungsten-iron shot is a blend of tungsten powder and iron powder pressed into
the shape
of a pellet and heated to bond the material. Methods of manufacturing this
type of shot are
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CA 02432820 2003-06-19
described in United States Patent No. 5,831,188 (Amick). Tungsten-iron shot is
roughly 95
per cent as dense as lead, which results in excellent ballistic properties..
However, this type
of shot is limited in the available shot sizes, and is quite expensive by
comparison.
Tungsten-iron shot is also extremely hard, and like steel, tends to penetrate
through game
with a reduced energy transfer, and can damage the barrels of some older
shotguns.
Tungsten-polymer shot is manufactured by mixing powdered tungsten and other
metals with
a polymer, such as nylon, and then pressing and heating the mixture to form
pellets. This
type of shot, manufactured by Kent Cartridge Manufacturing Company l.td. under
the name
Tungsten MatrixTM, and by Federal Cartridge Company under the name of
Tungsten-Polymer, is designed and constructed to have the same density as
lead, and is
safe to use in older shotguns. However, these tungsten-polymer products are
quite
expensive.
Additionally, these tungsten-polymer shot materials, as well as those
described in the prior
art, such as United States Patent No. 6,216,598 (Godfrey Phillips), tencl to
be too brittle for
effective game hunting when heavier shot is required. This is because
relatively low density
polymer materials are used to increase the hardness of the shot material.
Therefore, higher
density shot material must comprise reduced quantities of polymer, thus
increasing the
brittleness of the shot.
Other references pertaining to tungsten-polymer shot, including United States
Patents No.
5,719,352 (Griffin), and 6,048,379 (Bray et al.), fail to address or improve
upon the limitations
of current tungsten-polymer shot materials.
Tungsten-nickel-iron shot is a type of non-toxic shot which has recently been
approved for
use in Canada and the United States. ENVIRON-Metal Inc. markets a version
under the
name HEVI-SHOTT"". While tungsten-nickel-iron shot is more dense than lead
shot, and has
good ballistic properties, the raw materials are expensive, causing the cost
of this type of
shot to be high. Additionally, versions of this type of shot, such as those
described in United
States Patent No. 6,527,880 (Amick) can be too hard to shoot in older types of
shotguns.
Non-lead materials may also be used to replace the lead cores found in
conventional
jacketed hunting bullets, and to produce solid lead-free bullets. These forms
of non-toxic
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CA 02432820 2003-06-19
ammunition are certainly desirable in view of proposed bans on lead bullets in
Europe and
Asia.
Presently, there are few manufacturers of non-toxic bullets designed for
hunting. These
bullets generally are made of copper or copper alloys, and some have a polymer
insert in
the frontal cavity. United States Patent No. 5,131,123 describes a method for
manufacturing
a bullet made out of solid metal, such as copper. However, since copper is
less dense than
lead, finished copper bullets must be longer than their lead counterparts.
The increased length of copper bullets presents a significant problem for the
accuracy of
these bullets. This is because longer bullets are less stable during flight,
which reduces the
accuracy. However, increasing the twist of a bullet during flight can increase
the stability,
which gives better accuracy. Therefore, for a copper bullet to have a
comparable accuracy
to its counterpart lead bullet, it requires more twist. Accordingly, for
shooters to achieve good
accuracy with such bullets, they must buy custom-made barrels for their rifles
which provide
the required twist. Since most shooters cannot afford to buy custom-barrelled
rifles, copper
bullets are often used with sub-standard accuracy.
Other examples of non-toxic bullets have been described in United States
Patents No.
5,616,642 (West, et al.), 6,090,178 (Benini), and 5,399,187 (Mravic, et al.).
While the bullets
described in these documents are typically constructed of non-toxic metal
particles and metal
or polymer binders, they are intended for use in shooting ranges, rather than
hunting
applications. These frangible bullets mimic the ballistic properties of lead
bullets, but are
intended to disintegrate on impact to reduce the hazard of ricocheting bullet
fragments within
the range. Therefore, the brittleness of these bullets renders them
ineffective for hunting
game. Additionally, it has been found that these bullets sometimes crack
during the crimping
operation.
In light of the known deficiencies of materials currently used for
manufacturing non-toxic
hunting ammunition, there exists the need for a new material having a density
comparable
to that of lead, which is sufficiently malleable so that it does not damage
older weapons, and
provides a high level of energy transfer to the target, but which is not
brittle.
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CA 02432820 2003-06-19
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new
com~>osition and method
for manufacturing non-toxic projectiles which have superior ballistic
properties to other
non-toxic projectiles, are safe for use in most hunting firearms, and less
expensive to
manufacture than other non-toxic projectiles.
According to one aspect of the present invention, there is provided a
composition comprising
metal particles and rubber for manufacturing non-toxic shat, bullets and
bullet cores.
The metal particles which may be used in the composition may comprise one or
more metals
including copper, tungsten, iron, tin or any other non-toxic metal having a
high specific
gravity. A particularly preferred metal for use in this composition is
tungsten. Additionally, the
metal particles may be in the form of powders, granules, flakes, another
compactable form,
or a combination thereof.
The varieties of rubber used in the composition are moldable, uncured, rubbers
which have
a sufficiently low viscosity to be thoroughly mixed with the metal particles,
and may be
synthetic or natural. The viscosity of the rubber ranges from about 48 KU to
about 125 KU,
although the preferred viscosity ranges from about 75 to 80 KU. Rubber:> which
are suitable
for the composition of the present invention include natural rubber, neoprene,
polyisoprene
and styrene-butadiene rubber. Natural rubber is particularly preferred.
The ratios of metal to rubber used in the present invention range from about
25 to about 1
parts by weight for the metal particles and about 25 to about 1 parts by
weight for the rubber,
and depend upon the metal used. However, a ratio of 15 parts metal particles
to 3 parts
rubber is advantageously used in the preferred method of manufacturing non-
toxic shot.
When manufacturing bullet cores and solid, non-jacketed bullets, a ratio of 7
parts metal
particles to 2 parts rubber is used for the preferred embodiment.
The preferred size of the metal particles used in the present invention ranges
from
approximately 5 to 10 microns for non-toxic shot, while the preferred particle
size used for
manufacturing non-toxic bullet cores and solid, non aacketed bullets ranges
from
approximately 20 to 25 microns. A particle size of 5 microns is especially
preferred for non-
5
CA 02432820 2003-06-19
toxic shot, and a particle size of 25 microns is especially preferred for the
bullet cores and
solid, non-jacketed bullets of the present invention.
According to a second aspect of the present invention, there is provided a
method for
manufacturing non-toxic shot comprising the steps of:
mixing metal particles and moldable, uncured rubber to form a matrix,
molding the matrix under pressure in a shot-molding apparatus, and
curing the rubber to form a non-toxic shot,
wherein the non-toxic shot has a density ranging from approximately 10.5 g/cm3
to 13.5
g/cm3 and a hardness ranging from about 2 Bh to about 20 Bh on the hardness
scale.
In one embodiment of the method for manufacturing non-toxic shot, the rubber
within the
matrix is cured following removal of the shot from the shot-molding apparatus.
In another embodiment of the method for manufacturing non-toxic shot, the
rubber within the
matrix is cured prior to removal of the shot from the shot-molding apparatus.
In a further embodiment of the method for manufacturing non-toxic shot, the
finished shot
is plated with a metal selected from the group consisting of zinc, copper,
copper alloy, iron,
steel, antimony, nickel and tungsten. The weight of the applied plating is
preferably less than
1 % of the total weight of the shot. In a particularly preferred embodiment,
the weight of the
applied plating is about 0.0999% of the total weight of the plated shot.
According to a third aspect of the present invention, there is provided a
method for
manufacturing non-toxic bullet cores comprising the steps of:
mixing metal particles and moldable uncured rubber to form a matrix,
placing the matrix into a die or mold,
pressing the matrix to form a core,
seating the core inside a bullet jacket,
curing the rubber, and
point-forming within a point-forming die to produce a bullet,
wherein the bullet core has a density ranging from approximately 5 glcm'~ to
13.5 glcm3 and
a hardness ranging from about 2 Bh to about 20 Bh on the hardness scale.
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In the method of manufacturing non-toxic bullet cores, the core may be formed
in the
pressing step by swaging the matrix in a core-swaging die, followed by a
separate step
wherein the formed core is seated inside a bullet jacket. Alternatively, the
pressing and
seating steps may be performed simultaneously by pressing the matrix vrithin a
bullet jacket
using a core-seating die.
The rubber within the matrix may be cured before or after the point-forming
step, although
it is preferred that the curing occurs after the point-forming step.
According to a fourth aspect of the present invention, there is provided a
method for
manufacturing solid, jacketless, non-toxic bullets, comprising the steps of:
mixing metal particles and moldable uncured rubber to form a matrix,
placing the matrix into a die or mold,
pressing the matrix to form a bullet, and
curing the rubber,
wherein the bullet has a density ranging from approximately 5 g/cm3 to 13.5
glcm3 and a
hardness ranging from about 2 Bh to about 20 Bh on the hardness scale.
In this method, the rubber within the matrix may be cured prior to removal of
the bullet from
the mold, or following removal of the bullet from the mold.
In particularly preferred embodiments, the non-toxic shot has a density of
approximately 11.3
g/cm3, the bullet cores have a density of approximately 11 g/cm3 and the
solid, non-jacketed
bullets have a density of approximately 11 glcm3.
In the methods of manufacturing shot and solid, non-jacketed bullets, the
molding pressure
ranges from 26,000 PSI to 32,000 PSI, although a pressure of 28,000 PSI is
particularly
preferred. In the method of manufacturing bullet cores, the molding/seating
pressure ranges
from 4,000 PSI to 6,000 PSI, but is optimally 5,000 PSI.
In the methods of manufacturing shot, bullet cores arid solid, non-jacketed
bullets, the rubber
material within the matrix is cured at a temperature ranging from about 235 to
about 335
degrees I=ahrenheit, for a duration ranging from about 1 to 20 minutes. In
preferred methods
of manufacturing shot and solid, jacketless bullets, the optimal curing time
is about 12
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CA 02432820 2003-06-19
minutes at about 294 degrees Fahrenheit. The preferred curing condition for
manufacturing
bullet cores is about 11 minutes at about 275 degrees Fahrenheit.
The preferred hardness of the shot and solid, jacketless bullets manufactured
according to
the invention is about 8 Bh, whereas the preferred hardness of the bullet
cores is preferably
about 5 Bh.
BRIEF DESCRIPTION OF THE DRAWINGS
1o Embodiments of the present invention will be further described, by way of
example, with
reference to the accompanying drawings, in which:
Figure 1 is a diagrammatic cross-sectional view of a shot molding apparatus;
Figure 2 is a diagrammatic cross-sectional view of a finished shot produced
using the method
of the present invention;
Figure 3 is a diagrammatic cross-sectional view of a matrix core of the;
present invention
being seated into a bullet jacket;
Figure 4 is a diagrammatic cross-sectional view of a matrix core of the
present invention
seated inside a bullet jacket;
2o Figure 5 is a diagrammatic cross-sectional view of a solid, non-jacketed
bullet being formed
with the matrix material of the present invention; and
Figure 6 is a diagrammatic cross-sectional view of a finished solid bullet
produced using the
method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In order to overcome the disadvantages of known non-toxic materials and
methods for
manufacturing hunting projectiles, the inventors of the present invention have
developed a
novel composition and method for manufacturing non-toxic projectiles which
have a density
higher than or comparable to the density of lead, without increasing the
brittleness of the
material.
The novel composition comprises non-toxic metal particles having a specific
gravity greater
than 3 glcm3 and uncured moldable rubber. These materials are mixed in ratios
which are
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CA 02432820 2003-06-19
defined by the requirements of a particular hunting application, in order to
produce shot,
bullet cores and solid bullets.
For the purposes of the present invention, it is to be understood that the
metal particles used
in the matrix composition may be in the form of metal powder, granules,
flakes, another
compactabie form, or a combination thereof, providing that they are
compactable and have
a sufficiently high density. Metal particles which are particularly useful are
those which
comprise metals having high densities, such as copper, tungsten, iron, and
tin, although
other non-toxic metals may be used. Tungsten metal particles are especially
preferred.
When compared to the size of metal particles used for manufacturing bullet
cores and
bullets, the size of the metal particles used for manufacturing shot is
significantly smaller.
This reflects the relatively small size of shot, and the requirement for the
metal particles to
compact tightly. For bullet cores and solid, jacketless bullets, expansion is
very important,
and larger particles have been found to be more advantageous versus smaller
particles. The
preferred size of the metal particles used for manufacturing shot ranges
between about 5 to
10 microns, while methods for manufacturing bullet cores and solid bullets
preferably utilise
metal particles with a size ranging from about 20 to 25 microns. For shot, a 5
micron particle
size is preferred, whereas 25 micron particles are advantageously used for
manufacturing
bullet cores and solid, jacketless bullets.
It is also to be understood that the rubber which is used in the composition
may be a natural
or synthetic rubber providing that it has a sufficiently low viscosity that
the uncured rubber
can be thoroughly mixed with the metal particles. Some examples of rubt~er
materials which
may be used to manufacture the projectiles of the present invention include
natural rubber,
neoprene, polyisoprene and styrene-butadiene rubber, although combinations
thereof may
also be used in some embodiments. The rubber material which is especially
preferred for the
purposes of this invention is natural rubber.
3o The viscosity of the uncured rubber may range from approximately 48 Krebs
Units (KU) to
approximately 125 KU. The preferred viscosity is between about 75 and 80 KU,
slightly
thinner than ordinary household paint. Heavier or larger particles may require
a more fluid
rubber, which may require the addition of a thinning agent. While thinning
agents are not
required for the preferred embodiments of the invention, it is to be
understood that addition
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CA 02432820 2003-06-19
of suitable thinning agents to the rubber in order to increase its fluidity is
also provided by the
present invention.
The relative amounts of metal particles to rubber in the novel composition
depend largely
upon the particular metals and rubbers being used. For instance, copper
particles may be
mixed with rubber in a completely different ratio compared to tungsten
particles. Furthermore,
the ratio of metal particles to rubber also depends upon the application of
the desired
product. If the end product is intended to have properties similar to lead,
then the metal to
rubber ratio will generally be the same for shot, bullet cores and solid
bullets. However, in
other cases a higher ratio of rubber to metal may be required, especially when
manufacturing
bullet cores. For instance, in order to achieve favourable bullet balance, a
core which is
lighter than lead is often desirable. Advantageously, the ratios of metal to~
rubber used in the
present invention range from about 25 to about 1 parts by weight for the metal
particles and
about 25 to about 1 parts by weight for the rubber, and depend upon the metal
used. The
preferred non-toxic shot has a ratio of 15 parts metal particles to 3 parts
rubber, and the
preferred bullet cores and solid, jacketless bullets have a ratio of 7 parts
metal to 2 parts
rubber.
The composition of the present invention may be used to manufacture non-toxic
hunting
projectiles, such as shot for shotguns, bullet cores and solid bullets. When
manufactured
according to the following methods, these projectiles have a density
comb>arable to or higher
than the density of lead, and have excellent ballistic properties.
In the novel method of manufacturing shotgun shot, the metal particles and
uncured
moldable rubber are mixed together to form a matrix in a particular weight
ratio such that the
required density is achieved. For instance, a weight ratio of 15 parts metal
particles to 3 parts
rubber is frequently used in order to meet the specific ballistic requirements
of shot. After the
correct proportion of metal particles and rubber is mixed, the matrix is
forced into a mold or
die having an array of shot cavities cut or drilled therein. A minimum
pressure of about 5,000
PSI is normally required for proper molding of the shot, although the shot is
preferably
molded at pressures between about 26,000 PSI and about 32,000 PSI, and most
effectively
at a pressure of about 28,000 PSI. The shot may remain in the molding
apparatus during the
curing process or may be removed from the apparatus and then cured.
CA 02432820 2003-06-19
In certain embodiments, the finished shot may be plated with copper, copper
alloy, zinc,
nickel, iron, steel, antimony, tungsten or any other non-toxic metal which is
suitable for metal
plating. The shot is generally plated using standard electroplating processes
that are known
in the art. Although plating is not essential for the production of non-toxic
shot in accordance
with the invention, it is often performed in order to increase the hardness of
the shot, and to
help the shot flow easier when dispensing.
The actual plating weight depends upon the shot size. For example, a #6 shot
will have less
plating than a #2 shot. In all cases, the weight of the plating is preferably
less than 1 % of the
total weight of the plated shot, in order to comply with current regulations
enforced by the
United States Fish and Wildlife Service. The preferred plating weight is about
0.0999% of the
total weight of the plated shot.
During the manufacturing process, the hardness or brittleness of the shot can
be controlled
by adjusting the time and temperature of the curing process without reducing
the density of
the shot. This is particularly advantageous when high density shot is
required, since the
amount of high density metal particles may be increased without causing the
shot to become
brittle.
fn the novel method of manufacturing non-toxic bullet cores, metal particles
and moldable,
uncured rubber are mixed together to form a matrix in ratios specific to the
properties of the
desired product. The metal particle/rubber matrix is then placed in a core-
farming die or mold
and compressed at a pressure ranging from about 4,000 PSI to about 6,000 PSI
to form the
desired core. However, a pressure of about 5,000 PSI is especially preferred.
The core is
cured, and then seated inside a jacket, followed by finishing of the bullet
using a point-
forming die.
In this method, the bullet core may be compressed inside a core-swaging die
and then
seated inside a bullet jacket. Alternatively, the pressing and seating steps
may be performed
simultaneously by pressing the matrix within a bullet jacket using a core-
seating die.
The rubber within the core may be cured before or after the point-forming
operation.
However, it is frequently advantageous to cure the rubber after the point-
forming operation,
particularly when manufacturing highly dense bullet cores. This is because the
cores often
become too hard after curing to be effectively finished in the paint-forming
die.
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CA 02432820 2003-06-19
In a preferred embodiment, the bullet core is finished to have an open tip
profile. However,
other profiles such as hollow point, flat point, round nose and other tip
profiles are within the
parameters of the present invention.
In the method of manufacturing solid, non jacketed bullets which are non-
toxic, metal
particles and moldable, uncured rubber are mixed together to form a matrix
using ratios
specific to the properties of the desired product Following mixing of these
materials, the
matrix is placed inside a mold or die having the shape and size of the desired
bullet. The
matrix is then pressed at a minimum pressure of about 5,000 PSI. However, for
optimum
molding of the solid bullet, the molding pressure ranges from about 26,000 PSI
to about
32,000 PSI, and is preferably about 28,000 PSI. The rubber within the matrix
may be cured
during the molding phase or cured after the bullet is removed from the molding
apparatus.
The conditions used for curing the rubber within the matrix are particularly
important, and
care must be taken to ensure that the appropriate curing time and temperature
are used
when manufacturing the shot, bullet cores and solid, non-jacketed bullets of
the present
invention. While the preferred curing conditions may vary depending on the
rubber which is
used, the rubber within the matrix is advantageously cured in a heat-
controlled oven at a
temperature ranging from 235 to 335 degrees Fahrenheit, for a duration ranging
from 1 to
20 minutes. Alternatively, the curing process may be performed in a hydraulic
heated press
with a temperature ranging from 260 to 330 degrees Fahrenheit, or in an
autoclave
pressurized to 40 PSI with a temperature ranging from 250 to 320 degrees
Fahrenheit. In the
preferred methods of manufacturing shot and solid, jacketless bullets, the
optimal curing
time is about 12 minutes at about 294 degrees Fahrenheit. The preferred curing
condition
used in the method of manufacturing bullet cores is about 11 minutes at about
275 degrees
Fahrenheit.
Presently, heat is the preferred means for curing of the rubber. However, it
is conceivable
that curing of the rubber using chemical curing agents may also be used within
the scope of
the present invention.
In the methods for manufacturing non-toxic projectiles described above, <;are
must be taken
to ensure that the pressure does not exceed the recommended upper iirnit. For
instance, if
too much core seating pressure is used, it may be difficult to remove the
bullet from the core
seating die, thus distorting the bullet somewhat. Additionally, excessive
pressures can cause
12
CA 02432820 2003-06-19
the die to break when the swaging pressure approaches the die breaking
pressure. This is
particularly relevantwhen manufacturing shot or solid bullets, since high
pressures are used.
The projectiles which are manufactured in accordance with the methods outlined
above must
meet certain ballistic properties. For instance, the shot should be hard
enough that upon
ignition of the ammunition, the shot is not altered in terms of its shape.
This is important
because "unround" shot is detrimental to shot patterning. However, the shot
must not be so
hard as to cause it to be harmful to shotgun barrels. The projectiles
manufactured in
accordance with the present invention will not damage the barrels of older
firearms, but are
not brittle. When using the methods described herein, the resulting
projectiles have a
hardness ranging from about 2 Bh to about 20 Bh on the hardness scale. The
preferred
hardness of the shot is about 8 Bh, which is close to the hardness of 3%
antimony hardened
lead. The solid, jacketless bullets are also preferred to have a hardness of
approximately 8
Bh. However, the bullet cores manufactured using the method of the present
invention
preferably have a hardness of 5 Bh, which is the same hardness as pure lead.
The non-toxic shot manufactured according to the present invention has a
density ranging
from approximately 10.5 g/cm3 to 13.5 glcm3. However, it is preferable that
the density is
slightly higher than the density of lead, or approximately 11.3 glcm3. The
bullet cores should
have a density close to the specific gravity of lead, and similar
malleability. This is mainly due
to the many different bullet manufacturing methods, so if lead can be
substituted with a very
similar core material, a more accurate result will be achieved when using
different
manufacturing methods. Accordingly, the density of the bullet cores of the
present invention
have a density ranging from about 5 g/cm3 to about 13.5 glcm3, and optimally
about 11
glcm3. In regards to solid bullets, it is also favourable to produce a product
having a similar
density and malleability to lead. However, if a shooter is concerned with
accuracy, such as
during target shooting, a metal with a lower specific gravity is preferable.
In such cases,
copper is generally used instead of heavier metals such as tungsten. The
bullets
manufactured according to the present invention have a density ranging from
about 5 glcm3
to 13.5 glcm3, although the preferred bullets have specific gravities very
close to that of lead,
or approximately 11 g/cm3.
With reference to the drawings, preferred embodiments of the method s of
manufacturing
non-toxic shot, bullet cores and solid bullets will be described in further
detail.
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In the method of manufacturing non-toxic shot of the present invention, non-
toxic metal
particles 6 and rubber 5 are mixed together to form a matrix. The matrix is
then forced via
injection orifice 3 into a die or molding apparatus 1 having an array of shot
cavities 2 cut or
drilled therein (Figure 1 ). A minimum pressure of 5,000 PSI is required for
proper molding
of the resulting shot 4. The rubber 5 in the matrix is then cured. The shot ~
may remain within
the molding apparatus 1 during the curing process, or the shot 4 may be
removed from the
molding apparatus 1 prior to curing the rubber 5. The resulting finished shot
4 comprises a
dense matrix of metal particles 6 and cured rubber 5 (Figure 2).
The finished shot 6 may also be plated with metal or metal alloys, such as
copper, zinc,
nickel or any other non-toxic metal. This process is performed using known
electroplating
techniques, and is performed to produce a shot having a plating weight less
than 1 % of the
total weight of the finished shot 4.
In the method of manufacturing non-toxic bullet cores of the present
invention, non-toxic
metal particles 6 and rubber 5 are mixed together to form a matrix. In this
preferred
embodiment, a specific amount of the matrix is placed in a core seating die 9
and
compressed between an external punch 7 and an internal punch 8 at a minimum
pressure
of about 4,000 PSI. The bullet core 11 is seated directly inside a metal
bullet jacket 10 using
the core seating die 9 (Figure 3). Alternatively, the bullet care 11 may be
swaged separately
in a core swaging die and seated inside a metal bullet jacket 10 in a separate
step. The
rubber 5 in the matrix is then cured, and the resulting bullet is point-formed
using a point-
forming die. In another embodiment of this method, the rubber 5 within the
matrix of the
bullet core 11 may be cured after the point-forming process.
In the method of manufacturing solid, jacketless, non-toxic bullets of the
present invention,
non-toxic metal particles 6 and rubber 5 are mixed together to form a matrix
in a specified
ratio. Following mixing, the matrix is placed inside a bullet-forming die 12
and compressed
at a pressure of at least 5,000 PSI by external punch T and internal punch 8'
(Figure 5). It
is to be understood that external punch 7' and internal punch 8' are distinct
from external
punch 7 and internal punch 8 used for the forming of bullet cores 11, and are
selected based
of the desired shape and size of bullet 13. The rubber 5 within the matrix of
bullet 13 may be
cured during the molding step, or after the bullet 13 is removed from the
bullet-forming die
12.
14
CA 02432820 2003-06-19
The foregoing are exemplary embodiments of the present invention and a person
skilled in
the art would appreciate that modifications to these embodiments may be made
without
departing from the scope and spirit of the invention.
