WO1998040675A1

WO1998040675A1 - Plated projectile for use in subsonic ammunition

Info

Publication number: WO1998040675A1
Application number: PCT/US1998/004998
Authority: WO
Inventors: Harold F. Beal
Original assignee: Cove Corporation
Priority date: 1997-03-14
Filing date: 1998-03-16
Publication date: 1998-09-17
Also published as: CA2283839A1; EP0970329A4; EP0970329A1

Abstract

A projectile (18) for use in ammunition for a small-bore weapon which is operated in the semi-automatic or automatic mode and which is fired subsonically and without generating of audible sound during free flight of the projectile through air. The projectile, in one embodiment, comprises a tungsten/lead powder-based core (14) having a light metal plate (20) applied to the exterior surface thereof. A round of ammunition (24) incorporating the projectile (18) is disclosed which produces subsonic velocity of the projectile during flight and sufficient energy to consistently operate the bolt mechanism of the weapon. A method for the manufacture of the projectile is disclosed.

Description

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: Harold 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 1086 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 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 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 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 50% 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 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 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 semiautomatic 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 smallbore 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. 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 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 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.

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 5.56 mm cartridge, or a proportional weight projectile for a different size cartridge, such as a 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. 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 -10 and +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 remaining weight 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, powder (s) 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. 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 18 (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 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 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 .

It is to be recognized that in a given weapon having a rifled barrel, a projectile fired from the weapon will be 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 employs a one-in-seven twist, meaning that each land completes a 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 (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 longitudinal centerline (spin axis) is not attainable for projectiles that exceed a certain maximum length for a given 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 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 operating in the semiautomatic 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 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 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 less than 20 fps. The large variation in the standard 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 134 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 -250 + 400 and is also identified as a fine particle size oxidized polyethylene 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.

Claims

WHAT IS CLAIMED:

Claim 1. A projectile for an ammunition cartridge for use in a small-bore weapon operating in the semi-automatic or automatic firing mode and wherein the projectile of the cartridge is propelled at a subsonic velocity without generating audible sound during its free flight through air comprising

a core formed from a mixture of a heavy metal powder and a light metal powder, said mixture being cold- compacted to a density at least greater than the density of lead,

a plate of a light metal covering essentially all of the outer surface of said core, said light metal exhibiting lubricity properties between a projectile and a gun barrel,

said plate being of a thickness sufficient to develop an external diameter of the plated core substantially equal to the intended caliber diameter of the projectile.

Claim 2. The projectile of Claim 1 wherein said light metal plate is copper.

Claim 3. The projectile of Claim 1 wherein said core, prior to plating, has an external diameter that is smaller than the caliber diameter of the intended projectile.

Claim 4. The projectile of Claim 1 wherein said powder mixture is cold-compacted at a pressure greater than about 40,000 psi, and preferably about 50,000 psi.

Claim 5. The projectile of Claim 1 wherein said plated core is restruck in a die to a projectile precisely dimensioned and shaped for a given caliber weapon.

Claim 6. The projectile of Claim 5 wherein said plated core is restruck in a die at a pressure of about 50,000 psi.

Claim 7. The projectile of Claim 1 wherein said heavy metal powder is tungsten powder.

Claim 8. The projectile of Claim 7 wherein said tungsten powder is present in an amount of about 60%, by weight, with the remaining weight of the core being lead.

Claim 9. A projectile for an ammunition cartridge for use in a small-bore weapon operating in the semi-automatic or automatic firing mode and wherein the projectile of the cartridge is propelled at a subsonic velocity without generating audible sound during its free flight in air comprising

a core formed from a mixture of a heavy metal powder and a light metal powder, said mixture being cold- compacted to a density greater than the density of lead,

said core being of a geometry substantially like the desired geometry of the projectile for a given caliber weapon, and having an external diameter that is less than the desired caliber diameter of the projectile and a weight that is heavy for the intended caliber of the projectile,

a plate of a light metal covering substantially all of the outer surface of said core, said light metal exhibiting lubricity properties between a projectile and a gun barrel,

Claim 10. The projectile of Claim 9 wherein said light metal plate is copper.

Claim 11. The projectile of Claim 9 wherein said powder mixture is cold-compacted at a pressure greater than about 40,000 psi, and preferably about 50,000 psi.

Claim 12. The projectile of Claim 9 wherein said plated core is restruck in a die to a projectile precisely dimensioned and shaped for a given caliber weapon.

Claim 13. The projectile of Claim 11 wherein said plated core is restruck in a die at a pressure of about 50,000 psi.

Claim 14. The projectile of Claim 10 wherein said heavy metal powder is tungsten powder present in an amount of about 60%, by weight, with the remaining weight of the core being lead.

Claim 15. An ammunition cartridge for a small-bore weapon operated in a semi-automatic or automatic mode and wherein the projectile of the cartridge is propelled at a subsonic velocity from the weapon and the firing of the cartridge generates sufficient energy for the consistent successful operation of the bolt of the weapon without generating audible sound during its free flight in air, comprising a generally cup-shaped case having a closed end adapted to receive a primer therein and having an open end, said case having a geometry suitable for the receipt of the case within the chamber of the weapon,

a projectile disposed within the open end of said case, said projectile including a core formed from a mixture of a heavy metal powder and a light metal powder, said mixture being cold-compacted to a density greater than the density of lead,

said core being of a geometry substantially like the desired geometry of the projectile for a given caliber weapon, and having an external diameter that is less than the desired caliber diameter of the projectile, and a weight that is heavy for the intended caliber of the projectile,

said projectile closing said open end of said case and in combination with said case, defining a cavity within said case, a quantity of gun powder disposed within said cavity intermediate said projectile and the closed end of said case, said quantity of gun powder being

sufficient in quantity and burn rate to propel said projectile from said weapon at a muzzle velocity of not greater than the speed of sound under the existing ambient conditions of temperature and pressure, and

further being sufficient in quantity and burn rate, subsequent to firing of the powder, to develop a continuing gas pressure within the barrel of the weapon that is sufficient to operate the bolt mechanism of the weapon.

Claim 16. The ammunition cartridge of Claim 15 wherein said light metal plate is copper.

Claim 17. The ammunition cartridge of Claim 15 wherein said powder mixture is cold-compacted at a pressure greater than about 40,000 psi, and preferably about 50,000 psi.

Claim 18. The ammunition cartridge of Claim 15 wherein said plated core is restruck in a die to a projectile precisely dimensioned and shaped for a given caliber weapon.

Claim 19. The projectile of Claim 18 wherein said plated core is restruck in a die at a pressure of about 50,000 psi.

Claim 20. The projectile of Claim 15 wherein said heavy metal powder is tungsten powder present in an amount of about

60%, by weight, with the remaining weight of the core being lead.

Claim 21. A method for producing a projectile suitable for an ammunition cartridge for use in a small-bore weapon operating in the semi-automatic or automatic firing mode and wherein the projectile of the cartridge is propelled at a subsonic velocity without generating audible sound during its free flight through air comprising the steps of

forming a precursor core from a mixture of a heavy metal powder and a light metal powder by cold compaction of a quantity of said mixture to a density greater than the density of lead,

die-forming said precursor core into a core having a size and geometry substantially less than the desired size and geometry of the projectile to be formed,

plating a light metal onto the external surface of said core,

striking said plated core in a die having a cavity that is precisely dimensioned to the desired size and geometry of the projectile to be formed.

Claim 22. The method of Claim 21 wherein said heavy metal powder is tungsten powder and said light metal powder is lead and said tungsten powder is present in the mixture in an amount equal to approximately 60%, by weight, and the remainder of the mixture is lead.

Claim 23. The method of Claim 21 wherein said precursor core is die formed into a core at a pressure of about 50,000 psi, and said plated core is restruck in a die at a pressure of about 50,000 psi.