Note: Descriptions are shown in the official language in which they were submitted.
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PLATED PROJECTILE FOR USE IN
SUBSONIC AMMUNITION
RELATED APPLICATIONS
This application is a continuation-in-part of copending
application Serial No. 08/843,450, filed April 16, 1997,
entitled: SMALL BORE FRANGIBLE AMMUNITION PROJECTILE,
Inventor: Harald F. Beal and a continuation-in-part of
copending application Serial No. 08/815,003, filed March 14,
1997, entitled: SUBSONIC AMMUNITION, Inventor: Harold F. Beal.
FIELD OF INVENTION
This invention relates to ammunition for small-bore
weapons operated in the semi-automatic or automatic mode and
wherein the projectile of the ammunition travels at a subsonic
velocity from the weapon to the target and without generating
audible sound while in free flight. Particularly the
invention relates to a projectile for use in subsonic
ammunition for weapons of .50 caliber or smaller bore. As
used herein, the terms "weapon" and "gun" are at times used
interchangeably and are to be deemed synonymous unless
otherwise indicated or obvious from the context of their use.
BACKGROUND OF INVENTION
Most commonly, the projectile fired from a weapon,
particularly a rifle, leaves the muzzle of the weapon at a
speed that is greater than subsonic speed, i.e. at a muzzle
velocity of greater than approximately 1085 ft/sec. at sea
level under standard conditions of temperature and pressure.
The faster a projectile travels, the flatter is its trajectory
to its target. Also faster speeds of projectiles tend to
reduce the effects of lateral wind forces upon the path of the
projectile to its target. Therefore, for accuracy of delivery
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of the projectile to a desired target, commonly it has been
the practice to maximize the quantity of powder used to -
project a given weight projectile to its target consistent
with the permissible chamber pressure for a given weapon.
Minimization of projectile weight also has been employed to
provide greater projectile velocity for a given powder load.
Supersonic muzzle velocities, therefore, are the norm for most
small-bore rifles. Pistols, on the other hand, commonly
exhibit subsonic muzzle velocities. In the prior art, it is
also common to employ noise and/or flash suppressors on either
rifles or pistols. These devices function to reduce the sound
associated with the explosion of the gun powder in the
cartridge and/or the rush of gases from the muzzle of the
weapon, but, standing alone, suppressors are neither designed
for nor intended to reduce a supersonic velocity bullet fired
from a gun to a subsonic velocity, nor do suppressors
materially affect noise generated by the movement of a
projectile through air.
Projectiles traveling at supersonic speeds frequently
generate an audible sound during their free flight to the
target, a major source of which is wobble (yaw) of the
projectile during flight. This sound, and/or the sound
generated by the projectile breaking the sound barrier, can be
used to locate the source of the weapon from which the
projectile was fired. 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 traveling projectile.
Restricting the velocity of the projectile to a subsonic speed
provides only a partial solution to this problem.
A round of ammunition (at times synonymously termed a
"bullet" or a "cartridge") normally includes a case which
includes a primer, a quantity of powder contained within the
case, and a projectile held in the open end of the case. Upon
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the striking of the primer by the firing pin of the weapon
there is generated a flame which serves to ignite the powder
within the case, generating gases which expand and propel the
projectile from the muzzle of the weapon. Normally, the case
is geometrically shaped and sized to be contained within the
chamber of the weapon, and the projectile is of a diametral
dimension which allows it to fit in the breech end of the
barrel, and to eventually pass through the barrel upon firing
of the round. For many rifles, for example, it is common to
make the case of the round of ammunition of a size which will
provide for the maximumization of the force with which the
projectile is propelled from the weapon to the target. Thus,
it is common, for a round for a given caliber weapon, to
employ a case which will contain a maximum amount of powder,
hence the case has a large diameter relative to the diameter
of the projectile employed. Over time these cases have become
the "standard" case for a particular caliber weapon and
weapons of this caliber are chambered to accept this standard
case. Standards for the shape and size of a cartridge for a
given weapon, e.g. a rifle, of a given caliber are established
and published by Sporting Arms and Ammunition Manufacturers
Institute (SAMI).
In the many instances where the standard cartridge case
is of a diameter which is substantially larger than the
diameter of the bore of the weapon, that end of the case which
receives and holds the projectile of the cartridge is "necked
down" to a diameter suitable to engage and hold the projectile
in the case. For example, the outer diameter of the case for a
5.56 mm cartridge commonly is approximately .360 inch, and the
outer diameter of the projectile thereof is .224 inch. In any
event, any portion of the projectile that projects from the
end of the case is received within the breech end of the bore
of the weapon. In this situation, the circular shoulder
developed on the case by the necking-down operation serves as
a point of reference for the insertion of the cartridge in the
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chamber of the weapon. Specifically, the chamber of the
weapon is sized and shaped such that, when the cartridge is
fully and properly inserted into the chamber, at least the
juncture of the necked-down length of the case with the
circular base of the shoulder engages the breech end of the
barrel. With the cartridge in this position within the
chamber, that portion of the projectile which projects
outwardly from the end of the case is disposed within the bore
of the weapon. Through adjustment of the length of that
portion of the projectile which extends from the end of the
case, it is possible to select the distance by which the
projectile extends into the bore of the weapon. The degree of
this adjustment, however, is limited to that amount which will
not cause the overall length of the cartridge to be
unacceptably outside the SAMI specifications for the cartridge
when used in a semi-automatic or automatic weapon.
Heretofore, it has been proposed to produce subsonic
ammunition which comprises the "standard" case and projectile
for a given weapon, e.g. a rifle, and to merely reduce the
quantity of powder used to propel the projectile, to that
volume of powder which provides only sufficient energy to
propel the projectile at a subsonic muzzle velocity. The
round of ammunition thus produced is like a standard round of
ammunition for its intended weapon, but it is only about 500
or less filled with powder, leaving a substantial portion of
the interior volume of the case void of powder. This type of
subsonic ammunition is commonly fired as a "single shot" round
and is not capable of producing the energy required to operate
the bolt of a semi-automatic or automatic weapon.
A further major problem with this prior practice for the
manufacture of subsonic ammunition relates to the reduced
volume of powder within the case of the cartridge and the void
volume within the case. Specifically, when the weapon is
pointed (aimed} at a downward angle, relative to the
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horizontal, the powder within the case moves toward the
leading end of the case and adjacent to that end of the -
projectile which is inserted into the case. This serves to
form an air gap between the primer and the powder so that when
the primer is struck by the firing pin, there is a finite time
before the flame from the primer reaches and ignites the
. powder within the leading end of the case, and a finite time
elapsing before the burning powder generates sufficient gases
to propel the projectile from the weapon. Conversely, if the
weapon is aimed upwardly, relative to the horizontal, the
powder within the case moves toward the primer so that upon
the firing of the primer there is instantaneous ignition of
the powder and relatively quicker build up of the gases which
propel the projectile from the weapon. At intermediate angles
of aiming of the weapon, relative to the horizontal, there are
corresponding intermediate delays in the time required for the
projectile to be propelled from the weapon after the firing
pin has struck the primer. These degrees of delay are
extremely detrimental to the accuracy of delivery of the
projectile to an intended target. In some circumstances, the
delays in "firing" or "hang-fires" of the weapon have been
sufficiently long as to deceive the shooter firing the weapon
into believing that they have experienced a misfire.
Suspecting a misfire, the shooter may open the bolt of the
weapon to eject the suspected faulty round, whereupon the
round may explode with obvious serious endangerment to the
shooter.
In accordance with another aspect of the prior art
subsonic ammunition, it has been the practice to use fast-
burning powders, e.g. pistol powders. These powders
exacerbate the problem of erratic propulsion of a projectile
from the weapon by reason of the rapid build up of pressure
within the case and the rapid fall-off of the pressure once
the projectile leaves the case. As a consequence, the prior
art subsonic ammunition fails to provide the energy needed to
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operate the bolt in a semi-automatic or automatic weapon
and/or to lock the bolt in an open position upon the firing of
the last round in the magazine.
It is known in the art that the energy required to
operate the bolt of a weapon intended to be fired in a semi-
automatic or automatic mode involves the build-up of gas
pressure within the barrel of the weapon to the location of a
gas exit port near the muzzle of the barrel, such gas pressure
being adequate to operate the bolt mechanism.
It is therefore an object of the present invention
to provide an improved round of subsonic ammunition for small-
bore weapons.
It is another object to provide ammunition for a
small-bore weapon and which is consistently subsonic in
velocity from round to round of the ammunition.
It is another object to provide subsonic ammunition
which will effectively operate the bolt of an automatic or
semi-automatic weapon and which includes a projectile that
generates substantially no audibly detectable sound during its
free flight through air.
It is another object to provide a novel projectile
for subsonic ammunition.
It is another object to provide a method for the
manufacture of a novel projectile for subsonic ammunition.
Other objects and advantages of the present
invention will be recognized from the description contained
herein, including the claims and the drawings.
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SUMMARY OF INVENTION
In accordance with one aspect of the present invention
there is provided a round of ammunition for a small-bore
weapon wherein the projectile of the round exits the muzzle of
the weapon barrel at a subsonic velocity and which continues
its flight path to a target at less than a sonic velocity
without generating identifiable sound associated with the
flight of the projectile through air. Additionally, the
ammunition provides the energy required to operate the bolt of
a weapon fired in the semi-automatic or automatic mode. To
this end, the present inventor has discovered that by means of
a unique projectile combined with a powder of selected burn
rate, in a standard case, there can be attained the
objectives of subsonic velocity of the projectile, development
of the energy required to operate the bolt of a weapon fired
in the semi-automatic or automatic mode and elimination of
substantially all sound generated by projectile during its
free flight through air.
The novel projectile of the present invention comprises a
core formed from a mixture of a heavy metal powder and a light
metal powder by cold-compacting a quantity of the mixture in a
die at a high pressure. In one embodiment, the powder mixture
is initially compacted into a solid straight cylindrical core
precursor. Thereafter, the precursor is die formed at high
pressure into a core which is of substantially the desired
final geometry of the projectile, but which is of a diameter
less than the desired caliber diameter of the projectile.
This core is thereafter plated over substantially its entire
outer surface with a light metal which exhibits lubricity
properties between the projectile and a gun barrel. The
plating thickness is sufficient to produce an external
diameter of the projectile that is substantially equal to, but
not materially less than, the intended caliber diameter of the
projectile. In one aspect of the present invention, the
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plated core is restruck in a die which is precisely
dimensioned to produce a projectile having the desired caliber
diameter and geometry. In each of the die pressing
operations, the pressure employed is high, e.g., greater than
about 40,000 psi and preferably about 50,000 psi. Under a
pressure of this magnitude, at least portions of the powder-
based precursor or core (either plated or prior to plating)
will yield and be made to conform to the cavity of the die in
which the pressing is carried out. Notably, such high
pressure, following initial deformation of the powder-base
precursor or core within the die, further serves to redensify
the precursor or core to a density greater than the density of
lead.
In another aspect of the present invention, the
projectile of the present invention is maximized in weight for
a given length of a projectile for a given caliber weapon.
This action preferably takes the form of forming the
projectile from high-density metal powders as noted
hereinabove, maximizing the length of the projectile,
consistent with intended caliber of the projectile and the
twist of the lands in the barrel of the weapon for which the
ammunition is intended, and minimizing any variation in the
density of the projectile in any given plane normal to the
length of the projectile and in a direction radially outward
from the longitudinal centerline (spin axis) of the
projectile. When this unique projectile is inserted in the
open end of a standard case for a weapon of the intended
caliber, the projectile occupies a substantial portion of the
internal volume of the case, thereby diminishing that portion
of the internal volume of the case which is available to
receive gun powder, thereby permitting the case to be filled
to a higher percentage of its void volume. Further, the
inventor has found that use of a gun powder of medium burn
rate provides gas generation at a rate and of a volume which,
in combination with the heavy projectile, propels the
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projectile at a subsonic velocity while generating the energy
needed to operate the bolt of a weapon fired in the semi-
automatic or automatic mode. Still further, by maximizing
the length of the projectile, consistent with the twist of the
lands within the barrel of the weapon from which the
projectile is intended to be fire and in combination with
establishment of the center of gravity of the projectile
coincident with its spin axis, the projectile generates
substantially no audible sound during its free flight to a
target.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a side view of a projectile embodying various
of the features of the present invention;
Figure 2 is a side view of a geometrically shaped core
element embodying various of the features of the invention;
Figure 3 is a side view, in section, of the projectile of
Figure 1;
Figure 4 is a representation of a cartridge embodying
various of the features of the present invention; and
Figure 5 is a flow diagram of one embodiment of a method
for producing a projectile embodying various of the features
of the present invention.
Figure 6 is a schematic representation, part in section,
of a weapon employing a gas-operated bolt.
DETAILED DESCRIPTION OF INVENTION
In the present invention, a "heavy" projectile is
defined as a projectile having a density greater than lead,
e.g. about 12 or more g/cc, and a total weight of at least
about 134 grains, for a 5.5& mm cartridge, or a proportional
weight projectile for a different size cartridge, such as a
AMENDED SHEET
9
projectile of 250 grains for a .308 caliber cartridge and of a
density greater than lead. As noted, a preferred powder
exhibits a medium burning rate. For the present invention, a
"medium burning" gun powder is a gun powder that has a burn
rate substantially equal to the burn rate of HODGDON 380 gun
powder HODGDON H-380 is a fine-grained spherical gun powder.
Like all spherical gun powders, H-380 is a double base powder
that contains both nitroglycerine and nitrocellulose as the
base that creates the gas to propel the bullet through the gun
barrel. Each of the elements of the present invention is
selected in combination with the other elements to obtain
consistency of subsonic velocity from round to round of the
ammunition and provide the energy required for operating the
bolt of a semi-automatic or automatic weapon without the
projectile exceeding subsonic velocity, while also
substantially eliminating any sound generation associated with
the free flight of the projectile through air.
With reference to the Figures, the projectile 14 of the
present invention includes a core 18 which is metal powder-
based, meaning that the core is made up of a blended mixture
of metal powders and having a longitudinal centerline 22. In
the present invention, the preferred metal powders are
tungsten powder and lead powder. In the core of the present
projectile, the percentage of tungsten powder may range from
about 40$ to about 75~, and preferably 60$, by weight, with
the remainder of the mixture being lead. For the present
projectile, it is desired that the density of the core be
maximized, consistent with the ability to manufacture the core
from the powder mixture. Mixtures of these powders within the
stated ranges provide a core having a density materially
greater than lead, e.g. about 13-14 (g/cm3).
The preferred tungsten powder exhibits a particle size of
about between about 10 mesh and about 70 mesh and is the C and
M series available from Osram Sylvania of Morristown, NJ. One
suitable lead powder is that provided by Atlantic Engineers of
Bergenfield, NJ, having a mesh of about 325. In the mixture,
the tungsten powder represents between about 40 and 75$ by
weight, of the mixture, preferably 60$, by weight, with the
90 remaining weight
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of the mixture being lead powder. Other powder mixtures may
be employed but at the possible expense of attaining less than
maximization of the density of the projectile. Further, a
third, or more, powders) may be included in the mixture for
various purposes such as increasing or decreasing the hardness
or frangibility of the projectile. The powders of the mixture
are blended in a conventional "V" blender until thoroughly
mixed.
A portion of the blended powders is introduced into the
cavity of a die having a cylindrical die cavity. In the die,
the mixture of powders is cold-compacted at a pressure of at
least about 40,000 psi and preferably at a pressure of about
50,000 psi. Under these pressing conditions, the powder
mixture is densified and formed into a hard, self-supporting,
solid straight cylinder.
In a preferred embodiment, a quantity of the blended
powders is introduced into a die having a straight cylindrical
die cavity. In the die, the powder mixture is formed by
compaction of the mixture of powders at ambient temperature,
termed "cold-compaction" herein, into a core precursor 16.
A pressure of at least about 40,000 psi and preferably about
50,000 psi is employed. The temperature at which compaction
is effected may range below or above room temperature, but
preferably does not exceed the melting point of lead. Within
this range of temperatures, the lead is sufficiently ductile
as permits it to be squeezed between the tungsten powder
particulates and serve as a binder that holds the tungsten
particulates together in a predetermined geometrically shaped
core precursor. Under these pressing conditions, the powder
mixture is densified and formed into a hard, self-supporting
solid straight cylinder, in one embodiment. Typically, the
core precursor formed in this initial die-forming operation
has a density in excess of the density of lead and is very
hard.
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It will be recognized that tungsten powder particulates
are very hard and very abrasive. Tungsten particulates are
difficult to bond into a self-supporting body. Bare tungsten
projectiles will very quickly destroy a gun barrel due to
abrasion of the bore of the barrel by the projectile which is
propelled through the bore of the weapon. These properties of
the tungsten powder also cause it to be difficult to die-form.
High forming pressures, e.g. 50,000 psi, have been found to be
necessary for forming tungsten/lead powder particulates into
a body that will be sufficiently dense and have uniform
density as discussed herein.
The core precursor 16 is die-formed into a core I8 (see
Figure 2) which is of the desired general geometry desired for
the final projectile, but which is undersized, at least in
diameter (caliber), relative to the desired final diametral
dimension (caliber) of the projectile being formed. The
extent of undersizing of the core is a function of the desired
thickness of the light metal plating 20 to be applied to the
core. Generally, the extent of undersizing, hence the
thickness of the plating, is chosen to provide a plate that
has a thickness which is slightly greater than the height of
the lands in the rifled barrel of the weapon from which the
projectile is intended to be fired. For example, for a 5.56
mm weapon (e. g., a M-16 military rifle) a suitable plate
thickness would be about 0.025 inch thick to ensure that the
lands of the weapon would not be contacted by the metal
powder-based core of the projectile.
The pressure employed during this die-forming operation
is sufficient to disrupt and/or destroy bonds between the
powder particles of the core precursor such that the precursor
is caused to conform to the cavity of the die in which the
precursor is pressed to form the core. Pressure of at least
about 40,000 psi, and preferably about 50,000 psi, is employed
in this die-forming operation. Further, in this initial
12
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operation of forming the core from the precursor, the pressure
is sufficient to cause reestablishment of at least a portion
of the bonding between the powder particles of the newly
formed core as will permit the mechanical handling of the core
during further manufacturing operations, e.g., electro or
chemical plating of a soft metal plate onto the external outer
surface of the undersized core.
Thereafter, the die-formed undersized core 18 is plated
on its exterior surface with a layer (i.e. plate) 20 of a
relatively soft metal. Copper is a preferred metal for
plating onto the core. Preferably, the copper plating solution
employed is free of cyanide inasmuch as the inventor has found
that the somewhat porous core retains in its pores a portion
of the plating solution, and this solution tends to leach out
of the core over time and react with the copper plate to
produce unacceptable discoloration of the copper plate.
Plating of a soft metal onto a metal core is well known
in the art (U. S. Pat. No. 5,597,975, for example). Generally,
the cores are cleaned and thereafter plated employing a
conventional plating method which preferably does not include
cyanide in the plating solution. The various plating
conditions, such as temperature, time, etc. are selected to
lay down a layer of soft metal plate that uniformly plates the
exterior surfaces of the core with a soft metal plate of the
desired thickness.
Inasmuch as a plate having irregularities in its outer
surface or too great a thickness of the plate may cause the
projectile to jam in the barrel of the weapon, or preclude
chambering of the projectile in the weapon, following
application of the plate onto the core, the plated core is
restruck in a still further die. This latter die is
internally sized to the precise dimensions desired for the
final form and caliber of the projectile. Employing pressures
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of about 50,000 psi, this restriking of the plated core
functions to precisely size the plated core into the desired
projectile, including any needed adjustment to the geometry,
especially the outer diameter of the projectile. A result of
this resizing is some crushing of the powder-based core. In
this sizing operation, there is again reestablishment of at
least a substantial portion of the powder particle bonds that
are disrupted in the restriking operation, so that an overall
core density in excess of the density of lead is achieved in
the finally-formed, plated projectile. This restriking
operation performed upon the plated core also has been noted
to integrate the plate with the core itself. That is, the
strong and hard (e.g., tungsten) powder particles adjacent to
the outermost core particles appear to be somewhat embedded
within the softer metal of the plate such that the
disintegration of the plate and core upon the projectile
striking a target tends to produce small fragments of the
plate.
Figure 6 depicts a typical weapon 100 having a gas-
operated bolt 110. In the depicted weapon, the bolt is
mounted on a bolt carrier 104 that is slidably mounted within
the breechblock 106 of the weapon. A firing pin 108 is
mounted within and carried by the bolt. A gas flow channel
leading from the interior 109 of the barrel 110 of the weapon
to a chamber 112 near the rear end 114 of the bolt carrier is
defined by a first leg 116 which leads from the interior of
the barrel to a second leg 118, which, in turn, leads to the
chamber 112. Upon the firing of a cartridge within the
weapon, the projectile is propelled along the length of the
barrel. Once projectile has passed the first leg 116 of the
gas flow channel, expanding gas from the fired cartridge flows
through the leg, thence through the second leg 118 and into
the chamber 112 where the pressure from the expanding gas
forces the bolt rearwardly (away from the barrel) to open the
breech, eject the empty cartridge case, etc.
AMENaE~J SHEET
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It is to be recognized that in a given we p having a
rifled barrel, a projectile fired from the weapon will be
40 spinning about its longitudinal centerline at a rate
which is a function of the twist of the lands inside the
bore of the weapon barrel. By way of example, a M-16
military rifle such as depicted in Figure 6, employs a
one-in-seven twist, meaning that each land completes a
45 full turn within each seven inches of barrel length.
Thus, a projectile fired from this weapon at a velocity
of 1050 fps will be spinning at a rate of 108,000 rpm.
At this rate of spin, any deviation of the center of
gravity of the projectile from its longitudinal centerline
50 (i.e. its spin axis) 22 will result in the projectile
exhibiting wobble (yaw) during its free flight to a
target, hence generation of sound during flight. The
present inventor has found that absolute coincidence
of the center of gravity of the projectile with its
55 longitudinal centerline (spin axis) is not attainable for
projectiles that exceed a certain maximum length for a given
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during its free flight to a target. In this regard, it is
also to be noted that in the process of applying a plate onto
the core, it is important that the applied plate be uniform in
thickness so as to not cause the center of gravity of the
projectile to be unacceptably shifted away from the spin axis
of the projectile.
To this end, the compressive force applied in the die-
pressing of the powder mixture into a core precursor, in the
die-pressing of the core precursor into a core, and in the
restriking of the plated core in a die, is aligned with and
parallel to the longitudinal centerline of the precursor or
core or plated core. By this means, it is believed that
deformation of the precursor or core or plated core as
necessary to cause the object being pressed to conform to the
internal dimensions of the die is limited principally to the
extremities of the object, leaving the vast bulk of the object
radially unchanged, hence retaining the radial uniformity of
the density of the object substantially intact. It also is
believed that the high pressure employed in forcing the object
to conform to the internal dimensions of the die tends to
reconstitute a substantial portion of any bonding between
adjacent powder particles which is disrupted in the course of
deformation of the object as it is caused to conform to the
die interior. These factors are further believed to
significantly contribute to the observed absence of sound
generation by the projectile during its free flight to a
target by reason of the attained degree of coincidence of the
center of gravity and the longitudinal centerline of the
projectile of the present invention.
Cartridges for a 5.56 mm weapon of the type depicted
in Figure 6 operating in the semi-automatic mode were
fabricated and fired to test the velocity of the projectile
from each cartridge and the ability of the cartridges
to develop sufficient energy to consistently operate the
bolt of the weapon. In the manufacture of these
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twist of the rifling of a weapon so that there exists a
maximum length of a projectile for a given caliber projectile
fired from a given weapon, which will remain sufficiently
stable in free flight as prevents the projectile from
generating audible sound while in flight. Specifically, it
has been found that a projectile of a length greater than
about 1.12 inch fired from a M-16 military rifle becomes
unstable in flight to the extent that the projectile generates
audible sound. This length factor, plus the limitation
imposed by the caliber (diameter) of the projectile, produces
a limit on the permissible length of a projectile for a given
weapon, thereby limiting the permissible volume of a
projectile for the weapon. Accordingly, in the present
invention, the overall density of the projectile is important
in maximizing the weight of the projectile, but also of
importance is the attainment of maximum uniformity of density
of the projectile in a direction radially outward from the
longitudinal centerline of the projectile, taken in any given
plane normal to the longitudinal centerline of the projectile.
The absolute density of the projectile of the present
invention may vary from plane-to-plane, but radially about the
longitudinal centerline of the projectile, its density is
substantially uniform in any given plane.
Notably, even though the density of each projectile maybe
nonuniform from end-to-end of the projectile, in any given
plane of the projectile taken normal to the longitudinal
centerline of the projectile, the density of the projectile is
uniform in a direction radially outward from the longitudinal
centerline of the projectile. That is, within a given plane
the density is uniform about the spin axis of the projectile.
This aspect of each projectile is important in establishing
the center of gravity of the projectile substantially
coincident with the longitudinal centerline of the projectile,
(i.e., with the spin axis of the projectile) and thereby
reducing the likelihood of the projectile exhibiting yaw
CA 02283839 1999-09-13
~ ~~~3~1~
cartridges, there was chosen a standard case of brass metal.
The case 24 of these cartridges was loaded with a
Federal 205 Match primer 26 in the closed end thereof and
with 11.2 grains of H 380, a spherical-particle gun powder
28 from HODGDON Powder Co., followed by insertion of a
projectile 18 within the open end 30 of the case, thereby
closing the open end and providing an OAL of the cartridge
of 2.260 inch. The powder filled approximately 65~ of the
cavity defined in the case between the primer and the
projectile. This powder exhibited a medium burn rate. In
addition to its other properties, this powder exhibits
consistent burn properties at temperatures of between about 0°
and about 125° F.
Like cartridges were prepared employing other gun
powders, having either a slower and faster burn rate than
the H-380 powder. These latter cartridges, along with the
cartridges which included the H 380 powder, were fired
from a M-16 (5.56 mm) weapon of the type depicted in
Figure 6 operating in the semi-automatic mode. The barrel
length of the weapon was 14.5 inches. At least ten rounds
of cartridges made from each of these powders were fired.
The muzzle velocities of the several cartridges were
monitored employing standard chronograph techniques. Only
the cartridges made with the slowing burning H 380 powder
consistently provided subsonic velocities of the projectiles
thereof as evidenced by all 10 of the rounds exhibiting
subsonic velocities of their projectiles and successful
operation of the bolt of the weapon on every round, including
the final round which is intended to lock the bolt in its open
position. In each set of 10 rounds of the cartridges made up
with the powders other than H 380, there was one or more
rounds which exhibited a sonic velocity, failed to
successfully operate the bolt of the weapon, or the standard
deviation between the velocities of the 10 rounds varied
uncontrollably between about 50 to about 200 fps. The rounds
made up from the H 380 powder provided a standard deviation of
AMENDED SHEET
m
" CA 02283839 1999-09-13
-s
~4~~~ 1~~9
less than 20 fps. The large variation in the stan a
-deviation exhibited by those powders that were slower or
faster burning than the H 380 powder is unacceptable for
reliable-firing subsonic ammunition. Like cartridges were
fired with like results from a M-16 weapon having a 20 inch
barrel. In all tests in which the present projectiles,
employing H 380 powder, were propelled at a subsonic velocity,
there was no audibly detectable sound generated by the
projectile due to its movement through air.
Further cartridges were made up using the H 380 powder
and projectiles having less weight and tested as above.
Specifically, projectiles having weights of 100, 115 and 126
grains were made and tested. None of these cartridges fired
consistently subsonic with a standard deviation within an
acceptable range.
Cartridges containing 139 grain projectiles and made up
using H 380 powder were fired from the M-16 weapon having a
suppressor attached to the muzzle of the barrel thereof. The
projectiles from these cartridges also consistently were
subsonic in velocity and exhibited an acceptable standard
deviation. The cartridges further successfully operated the
bolt of the weapon. Moreover, the total sound emanating from
the firing of the weapon was almost nonexistent. No audibly
detectable sound was generated by the flight of these
projectiles through the air.
In one embodiment of the present invention, the
projectile may be made to be readily frangible upon
impact with a solid or semi-solid target. To this end,
there may be incorporated into the mixture of tungsten and
lead powders, up to about 0.10$, by weight of a micronized
polyolefin wax such as ACumist 12 available from Allied
Signal, Inc., of Morristown, NJ. This powder has a mesh
of between about 250 mesh and about 400 mesh and is also
identified as a fine particle size oxidized polyethylene
AI~EIVflED StIEET
1g
CA 02283839 1999-09-13
WO 98J40675 PCT/US98J04998
homopolymer. This powder has been found to inhibit bonding of
the metal powder particles to one another and therefore, in
the noted small quantities, does not materially adversely
affect the formability or acceptable strength properties of a
solid cylinder that is die-formed in the manner set forth
hereinabove. A micronized polyolefin wax and metal powders
mixture, when formed into a projectile core plated with a
light metal provides a projectile which performs in all
material respects like a projectile formed from the metal
powders without the wax powder, except with respect to the
frangibility of the projectile when it strikes a target. The
degree of frangibility of the projectile is a function of the
quantity of micronized polyolefin wax employed, but should not
exceed about 0.10%, by weight, in order to obtain a
sufficiently strong, self-supporting cylinder.
Firing tests of the present projectile to a solid target
produced little more than a dark spot on the target. No
fragments of the plate larger than approximately the same
order of size as the individual tungsten powder particles were
noted, but rather the plate disintegrated into substantially
nonvisually-identifiable particulates. Ricochet of the
projectile, or of fragments thereof, is essentially
eliminated. In crush tests performed on restruck projectiles
of the present invention over a range of pressure values
showed that the projectiles of the present invention collapsed
at compressive pressures as low as about 200 psi, thereby
indicating the relative frangibility of these projectiles.
19
