Patent Application
20080092768
The present invention is an armor piercing projectile used with small arms cartridges. The inventive projectiles are suitable for both hard and soft targets. The inventive projectile is intended to be used by homeland security or military personnel rather than civilians. Various design considerations were evaluated in the development of the inventive projectile and cartridge.
For both hard and soft target ammunition, the projectiles are designed to deposit the limited available energy within the target in order to achieve the desired terminal effect. In the case of effective soft target terminal effects, it is best to deposit all available energy into the soft target. In some applications, the projectile may be designed for a combination of both soft and hard targets. For example, if a particular soft target has the benefit of some form of intervening hard protection, then the projectile must be able to pierce the protective armor and deposit all of the remaining energy into the soft target.
There are other ammunition applications in which special projectile characteristics are required. For example, if firearms are being used to defend a ship or an aircraft, the projectiles must be able to injure a soft target, but not penetrate or damage the structural components of the vessel. Other specific ballistic performance requirements include a minimal shot line deflection projectile that would be used to accurately strike a target that is seen behind glass. Various other special use projectiles are contemplated.
The inventive cartridge is designed to function reliably and safely in the weapon. When filling the cartridge, the peak chamber pressures comply with the CIP and SAAMI specifications. The cup material properties, propellant burning rate and loading density also produce the required muzzle velocity without excessive pressure, blast, flash, flame or barrel fouling. The inventive projectile seats cleanly into the case mouth. This seating does not include any shaving, binding or buckling of the cartridge case. The inventive projectile is also able to withstand the high loads caused by feed-ramp impact and the sudden stop during auto and semi automatic chambering. The inventive cartridge is able to maintain its structural integrity under extremes of temperature and humidity.
This inventive projectile 259 is illustrated in more detail in
With reference to
One of the special features of the cup 301 is the chamfered leading edge 307 that is used to sheer through the sheath 309 when the projectile hits the target. The chamfered edge 307 is sharp and able to cut through sheath 309 material. In the preferred embodiment, the chamfer angle α is about 15°. In other embodiments, the chamfer angle may range from about 5° to 45°. The cup 301 may be made of brass and formed in a punching process from ribbon brass stock, or may be made on a manual lathe, CNC lathe or multi axis CNC mill.
With reference to
With reference to
With reference to
In addition to enhancing impact performance, a blunter tip allows more material and mass to be placed at the front of the core 351. In an embodiment, the core 351 is fabricated through a sintering process in which powdered tungsten and carbide particles are placed in a die. The powder is pressed into the final core shape and heated until the tungsten and carbide particles are partially melted and fused together. The resulting projectile has a density that is nearly equal to a solid core 351. Tungsten carbide has very high strength, hardness, rigidity and impact resistance. The compressive strength of the sintered tungsten carbide is also higher than melted and cast or forged metals and alloys. Tungsten carbide compositions range from two to three times as rigid as steel and four to six times as rigid as cast iron and brass.
With reference to
The cartridge with the inventive projectile is shot like a prior art cartridge. When the trigger is actuated, the firing pin ignites the primer 205 that causes the propellant 257 to rapidly burn. The expanding gaseous combustion products 257 cause the projectile 259 to separate from the casing 253 and travel through the bore. The outer diameter of the cup 301 engages the rifling form in the barrel of the firearm causing the projectile 259 to rotate about its center axis. The inventive projectile 259 is uniformly engraved by the rifling form causing the projectile 259 to rotate without any gas blow by, base deformation or excessive barrel fouling. The rotation stabilizes the projectiles 259 as they move through the air minimizing their dispersion. The rotational forces are transmitted from the sheath to the cup 301 and the core and the tight fit of the projectile 259 components causes all of the components to rotate together in a unitary manner improving the projectile stability.
With reference to
For the inventive projectile 259, the position of the Cg remains constant but the position of the Cp can vary dynamically with projectile velocity. The Cp is generally forward of Cg and the separation between Cg and Cp is known as the “static margin.” Projectiles with a smaller static margin generally have greater inherent dynamic stability. A high stability projectile has less drag than a low stability projectile and will better retain its velocity and kinetic energy further down range.
The rotation of the projectile influences the stability of the projectile. In general, the projectile's rate of rotation is proportional to the stability of the projectile. The rotation causes gyroscopic inertia that stabilizes the projectile and causes it to resist change in its orientation. If the projectile spins too fast it may be “over stabilized” and may remain in the orientation that it was fired. Over stabilization may be problematic if the projectile's nose does not follow the arcuate curvature of the projectile trajectory due to gravitational forces. This is not normally a problem for small arms fired over extremely short, close quarter battle ranges because the projectile trajectory will typically be very flat. Conversely, if the projectile does not have enough spin the projectile may be unstable and the aerodynamic drag forces will cause the projectile to rotate and eventually tumble through the air.
As discussed above, the position of the Cp is variable and changes based upon the velocity of the projectile. At supersonic velocities, the Cp is located farther back on the projectile than at subsonic velocities. The projectile may be more stable when the Cp is behind the Cg and less stable when the Cp is farther in front of the Cg. The Cp can be located at substantially the same point as the Cg, behind the Cg or in front of the Cg. In order to improve the stability of the projectile, the inventive projectile is designed to have as much of its mass in the core at the front of the projectile as possible.
The Cg of the inventive projectile is fixed but designed to be towards the front of the projectile. The core 351 is made of high-density material and the cup 301 and sheath 309 are made of much lower density materials. Because the sheath 309 and cup 301 are made of lighter materials, the core 351 primarily controls the location of the center of gravity. The tip 359 of the core 251 has a broad angle that is substantially different than the more traditional a long tapered and pointed tip. This blunter tip 359 provides more volume so that the tip 359 has more material and more mass. Since the core 251 is towards the front of the projectile 259 most of the mass is also towards the front of the projectile. With the Cg farther forward the inventive projectile 259 has a shorter static margin and has more stable external ballistics.
The terminal ballistics of the inventive projectile is also very different than the prior art projectiles. The components of the inventive projectile remain together until the projectile strikes the target. At contact, the cup 301 breaks the sheath 309 and the components separate. The terminal ballistics reaction of the projectile components will depend upon the type of target.
For a hard target, the projectile 259 will disassemble upon contact and only the core 351 may penetrate the target. The core 351 and the sheath 309 are the first to contact the target. The impact causes the chamfered edge of the cup 301 to cleanly shear the sheath 309 away from the high-density core 351. The sheath 309 may also break along the grooves 329 causing the conical section 323 to splinter into many smaller petals. The core 351 is then free to penetrate the hard target. Because the sheath 309 is sheared away very easily, the core 351 loses very little energy as it penetrates the target. The ability of the inventive projectile to penetrate hard targets is enhanced because only a minimal amount of energy is consumed as the high sectional density core frees itself from the sheath 309 and cup 301. The core 351 retains the remaining kinetic energy. Since nearly all of the kinetic energy remains with the core 351, the majority of the energy is directed towards the penetration of the hard target.
In many cases, the hard target is protecting a soft target. After the core 351 has completed its primary role of penetrating the hard or intervening target, the inventive core is designed to deposit all residual energy as quickly as possible into the underlying soft target. As the core 351 enters the soft target, it creates a cavity in the target media. The degree to which permanent and temporary cavitation occurs depends upon the size, shape, and velocity of the projectile core 351 as well as the nature of the soft target media. A wide core 351 that has a blunt shape, higher velocity, or any combination thereof will increase the width of the permanent cavity. Optimized temporary cavitation is best achieved by maximizing the projectile core's 351 frontal area through yaw, resulting in the greatest residual energy deposition rate.
A projectile having a long core and narrow body with a sharp pointed tip will crush only the tissue directly in front of a small portion of its diameter while tissue closer to the edge of the core and will simply flow around it and be pushed outwards. A core having a blunter, flatter tip generates a much larger “bow wave” as it uses more of its face to crush the target tissue, but loses velocity more quickly in the process and is more likely to remain within the target.
Rather than traveling straight through the soft target, the inventive core 351 is wide with a blunt tip. The core 351 is designed to lose stability causing it to tumble and rotate in yaw in the soft target. Ideally, the core 351 will rotate so that it travels sideways with the long axis perpendicular to the direction of travel. This rotation causes the core 351 to present its largest possible frontal area and cause the largest drag force on the projectile core 351 within the soft target. In addition to a single 90° rotation, the core 351 may continue to tumble and rotate within the soft target that also slows the core 351 and may prevent its exit from the target. This tumbling and yaw motion increases the frontal area of the inventive projectile core 351 causing it to decelerate rapidly. The tumbling action also causes explosive temporary cavitation and a permanent narrow channel cavity.
If a soft target is not protected by a protective layer or there is only a minimal intervening material over the soft tissue target, the core 351 and other projectile components can penetrate the target. As discussed above, the core 351 is designed to penetrate and then tumble within the target rather than passing through the soft target. The core 351 will rotate with a significant degree of yaw to present the increased frontal area greater drag so that the core deposits the bulk of its residual kinetic energy within the target. The instability of the core 351 within the soft target is achieved through various core 351 properties at the time of impact including: angular velocity (spin rate), length to diameter ratio, static margin and yaw angle at impact.
In addition to the core 351, the cup 301 and sheath 309 components of the projectile can also penetrate the soft target. Upon encountering an unprotected soft target, the inventive projectile exhibits a fundamentally different behavior to that observed when striking a hard target in that the core 351 remains integral with the cup 301. The cup 301 is a hard minimally deforming structure that is a full caliber diameter. When the projectile 359 first enters the soft target, for example, FBI ballistic gelatin (10% w/w at 4°C.), conical section 323 of sheath 309 immediately breaks free at the chamfer 307 of cup 301 as smaller fragments along the groove 329 form in sheath 309. The lightweight sheath's 309 petals decelerate rapidly in the soft target and as they have very little mass or kinetic energy, are less likely to produce internal injuries of any significance. These petals are usually contained within about the first 50 mm of travel into the FBI gelatin block. The core 351 is held firmly in the cup 301 by the remaining lower cylindrical section of sheath 309. The structural integrity of these remaining projectile components allows them to remain intact and move through the soft target as one piece. The “thumb tack” like appearance of the remaining projectile components causes them to tumble as one, through the soft target.
While the basic design of the projectile has been described, the kinetic energy package that is delivered to a target is governed by various physical factors including: the propellant mass, loading density and relative quickness (burning rate), the primer, the projectile mass, the range to the target and the maximum permissible chamber pressure. For hard target applications having a cartridge with a fixed energy package, the inventive projectile should generate the highest possible pressure at the projectile strike point in order to penetrate the armor. The sectional density (SD) of the core is defined as the ratio of a projectile's mass (m) to the square of its diameter (d) in accordance with the relationship SD=m/d2. A high SD is achieved by using a small frontal projectile area, with a high projectile mass. A long cylindrical core provides the highest mass to density ratio, but a conical forebody is needed to improve the hard target surface penetration. By making the point blunt, more mass is maintained in a minimal core diameter. Also the core should have a length and diameter that provides a strong structure. A thin core will tend to break, thus reducing the penetration capabilities.
Kinetic energy is defined by the formula Ekinetic=½ mv2, where m is the core mass and v is the core velocity. Thus, a projectile having a high core mass, high sectional density, high velocity and, therefore, high kinetic energy at impact, is able to exert a high force per unit area (pressure) at the target surface and have the greatest possible chance of hard target penetration.
The velocity is improved by using the fastest burning propellant with the highest loading density without exceeding the maximum permissible peak chamber pressure. The core mass is increased by using tougher, higher density core materials and lower density sheath and cup materials. As discussed, the core must also be very strong to avoid brittle fracture at impact. Sintered tungsten carbide is one of several suitable core materials as it's high density and strength combine to resist brittle failure at impact. Because the core contains the majority of the mass, the majority of the kinetic energy is in the core rather than the cup or sheath. The sectional density and kinetic energy are primary factors in penetration mechanics.
The internationally accepted standard medium for testing bullets for performance on soft tissue is ballistic gelatine. Tests have shown that properly prepared and calibrated 10% (by mass) aqueous gelatine at 4° Celsius (FBI ballistic gelatine) correlates very closely to observed performance in soft target muscle tissue. Injury severity is generally characterized by the dimensions of the temporary cavity, the maximum depth of penetration and the dimensions of the permanent cavity formed in the gelatine by the passage of a projectile. The size of the temporary cavity represents the maximum radial displacement that tissue experiences as it is violently displaced by the passage of a projectile. In an elastic medium such as muscle tissue, the temporary cavity undergoes a series of decaying pulsations until the tissue establishes a new equilibrium rest position that defines the permanent cavity. By definition, all tissue within the volume of the permanent cavity will have been crushed and destroyed and will need to be debrided. The length of the wound tract is simply how far through the tissue the projectile has penetrated.
Another characteristic of the inventive projectile is that the finely dispersed, toxic lead cloud typically seen in x-radiographs of soft tissue impacted by lead based projectiles is completely absent in gelatine struck by the inventive ammunition projectile.
While the inventive projectile can be made in any number of calibers that correspond to the diameter of the projectile, testing was performed on a 9 mm version of the inventive projectile. In this example, the midbody was made of yellow brass, the sheath was made of Delrin and the core was made of sintered tungsten carbide at nearly full density and minimal porosity. The chamfer formed in the rim of the cup was 15°. Bulletproof clothing such as vests are made of many energy absorbent, high strength layers of high strength fabric. Each layer of fabric is compression molded with a binder resin to form the composite of Spectra 900. Examples of suitable fabric include a polyethylene fabric such as Spectra 900 and Spectra 1000, available commercially from Allied Signal Corporation of Petersburg, Va. and Morristown, N.J. Also suitable is an aramid fabric such as Kevlar 29 and Kevlar 49 manufactured by Dupont. The resin binder can be liquid binder such as Shell Krayton resin, laminates or other fiber bonding structures.
For testing purposes, 100 layers of hand gun bulletproof material were placed in front of a 4 inch thick phone book and a block of FBI ballistic gelatin. During testing the core of the projectile was able to penetrate completely through the 100 layers of bulletproof material and the phone book. At the point of impact, the sheath is broken by the chamfer in the cup and the core is separated from the sheath and cup. The cup was recovered from the bulletproof material whilst core perforated the ballistic gelatin placed behind the protective layers. The shape of the permanent cavity created by the impact of the core indicated that the core was spinning when it entered the gelatin.
In a further series of trials, individual 9 mm projectiles were easily able to perforate 12 mm thick aluminum plate, 7 mm thick mild steel plate, 12 mm thick laminated glass and the anti intrusion bar in a modern car door. When fired at a fully inflated modern steel belted radial tire, a 9 mm projectile also easily perforated the tread, steel plies, the bead and the folded J-J section of the steel rim upon exit.
When fired directly square on, 9 mm projectiles were easily able to pierce a modern car laminated windshield and hit the designated aim point located 50 cm behind the windshield. When fired at a 40 degree oblique angle of incidence, 9 mm projectiles were easily able to pierce a modern car laminated windshield and hit the designated aim point located 65 cm behind the windshield. The 9 mm projectiles were also easily able to penetrate a 35 mm solid wooden door backed by another 30 mm of particle board. All shots in these trials easily perforated the 1.3 mm thick aluminum witness sheets placed behind each target.
When fired from a P35 Browning 9 mm pistol in the free standing position, the 9 mm cartridges chambered flawlessly from the magazine, then fired, extracted and ejected perfectly, with all shots meeting the essential dispersion requirements. At the end of a 26 shot trial, the Browning pistol barrel showed no sign of fouling.
Although the same basic cup, sheath and core design is used for ammunition projectiles of various different sizes, some special design factors must be considered for different calibers of ammunition. For example, because the case volume of the 9 mm Parabellum, also known as the 9 mm Luger, 9 mm NATO and the 9 mm×19, is very small, careful consideration must be given to the primary role and desired terminal effects of the projectile. For example, if the primary role is penetration, the core may have a mass that is proportionally larger than the other components. In order to accommodate the mass without altering the caliber, the length of the projectile may have to be extended. This extended length may be more stable traveling through a soft target with less yaw motion. However, since the primary objective is to penetrate the hard target, the design compromise is acceptable. It is contemplated that various other design alternations can be made.
In other embodiments, the primary purposes may be to hinder a soft target but minimize damage to the target. In these embodiments, the core may include a marker, an irritant, visual impairment or any other type of hindering mechanism. In these embodiments, the chamfer of the cup may break the sheath and cause the separation of the projectile components. This separation of components may cause the release of the core hindering mechanism such as a dye marker ink or irritant.
In other embodiments, the projectile may be able to penetrate a hard target and deliver a hindering mechanism through a protective layer. In this embodiment, a hindering mechanism may be placed within the core or behind the core. The core may penetrate the protective layer as described above and the hindering mechanism contained within, or behind the core may be released after the core has passed through the protective layer. For example, a gas irritant may be released by the core.
In the foregoing, a special purpose small arms ammunition system has been described. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
