Technical Field

[0001] The present disclosure relates generally to a mixtures of a thermoset polymer and powdered metal, and more specifically to a thermoset-based frangible projectile. Background

[0002] A cartridge or a round is a type of pre-assembled firearm ammunition packaging a proj ectile (or bullet), a propellant substance and an ignition device (primer) within a metallic, paper or plastic case that is precisely made to fit within the barrel chamber of a gun, for the practical purpose of convenient transportation and handling during shooting. [0003] A bullet is a kinetic projectile and the component of firearm ammunition that is expelled from the gun barrel during shooting. Bullets are made of a variety of materials such as copper, lead, steel, polymer, rubber and even wax. A traditional bullet’s projectile may have a lead core wrapped in a copper jacket construction. Bullet sizes are expressed by their weights and diameters (referred to as "calibers") in both imperial and metric measurement systems. The bullets used in many cartridges are fired at muzzle velocities faster than the speed of sound and thus can each travel a substantial distance to a target before a nearby observer hears the sound of the shot. Bullets do not normally contain explosives, but damage the intended target by transferring kinetic energy upon impact and penetration.

[0004] Frangible ammunition, sometimes informally called frangible ammo, is somewhat similar to traditional ammunition, except for the projectile. Frangible ammo is a type of ammo loaded with a special frangible bullet or projectile. A frangible bullet is generally constructed of a powder metal compressed or “sintered” into a bullet. This unique bullet construction provides an effective and lethal force with additional safety features for shooters, trainers, and marksmen. The main safety benefit frangible ammo provides is the bullet’s ability to shatter or disintegrate into a powder or tiny particles upon contact with a surface harder than itself.

This minimizes the bullet’s penetration of other objects. Tiny particles are slowed more rapidly by non-target environments such as air resistance, and accordingly, are less likely to cause injury or damage to persons and objects distant from the point of bullet impact.

[0005] Frangible bullets are used in reduced ricochet, limited penetration (RRLP) loads intended to reduce risk to friendly forces and innocent persons during close-quarters military or police actions in urban areas, aboard ships or aircraft, or in hazardous material environments like oil platforms and chemical or nuclear plants.

[0006] Most frangible bullets are subj ect to brittle failure upon striking a hard target. This mechanism has been used to minimize the tendency of malleable lead and copper bullets to ricochet from hard targets as large, cohesive particles. Frangible bullets offer improved safety for specialized combat simulation training involving firing at an array of multiple steel targets in various directions encountered while moving through a maze. Frangible bullets are also used in reduced ricochet, limited penetration loads intended to reduce risk to friendly forces and innocent persons during close quarters military or police actions in urban areas, aboard ships or aircraft, or in hazardous material environments like oil platforms and chemical or nuclear plants.

[0007] Powder metallurgy techniques fabricate bullets from mixtures of powdered metals compressed at room temperature to produce a high-density material. Mechanical interlocking and cold welding bond the metals together either pressed directly to shape, or into bar stock billets that can be swaged into projectiles, with or without jacketing. Alternative manufacturing techniques include heat treating or sintering powdered metals at temperatures below the melting point, or binding the powdered metal with an adhesive or a thermoplastic polymer in an injection molding machine.

[0008] The use of a thermoplastic for binding the powdered metal entails the use of injection molding machines which adds to the production cost. Furthermore, thermoplastic resin is highly viscous and tends to trap bubbles therein. The presence of bubbles lowers the density of the projectile. Accordingly, the projectile has a lower mass and hence a lower kinetic energy which is not desirable. [0009] There is, therefore, a need for a frangible proj ectile which overcomes at least some of the problems of the prior art.

Summary

[0010] In accordance with one aspect of the present disclosure, there is provided a process for making a frangible projectile. The process comprises mixing a predetermined amount of a thermoset polymer resin with a predetermined amount of powdered metal to produce a slurry mixture. The process includes pouring the slurry mixture into a mold and curing the slurry mixture.

[0011] In one embodiment, the process further comprises providing the predetermined weight of thermoset polymer resin.

[0012] In one embodiment, the process further comprises providing the predetermined weight of powdered metal.

[0013] In one embodiment, the thermoset is Polydicyclopentadiene (PDCPD).

[0014] In one embodiment, the powdered metal is copper. In another embodiment, the powdered metal is tungsten.

[0015] In one embodiment, curing the mixture comprises curing the slurry mixture under atmospheric air conditions. In another embodiment, curing the mixture comprises curing the slurry mixture under vacuum.

[0016] In one embodiment, curing the mixture comprises curing the slurry mixture under pressure. In one embodiment, curing the mixture under pressure comprises curing the slurry mixture in an autoclave.

[0017] In one embodiment, mixing the thermoset polymer resin with the powdered metal comprises injecting the thermoset polymer resin under pressure into the powdered metal. [0018] In one embodiment, mixing the thermoset polymer resin with the powdered metal comprises producing vacuum for drawing the thermoset polymer resin towards the powdered metal.

[0019] In one embodiment, the process is carried out under pressure. In another embodiment, the process is carried out in a vacuum.

[0020] In another aspect of the present disclosure, there is provided a mixture of a thermoset polymer mixed with a powdered metal for use as a replacement for lead.

[0021] In one embodiment, the mixture is produced by the above process.

[0022] In accordance with another aspect of the present disclosure, there is provided an ammunition round comprising a case, a propellant substance, an ignition device, and a frangible projectile. The case is sized to fit within the barrel of a gun or an artillery piece, has an open end, a closed end and an interior. The propellant substance is disposed in the interior of the case. The ignition device is arranged at the closed end of the case and configured for igniting the propellant substance. The frangible projectile is disposed at the open end such that when the ignition device is activated, the propellant substance causes the projectile to be propelled away from the closed end. The frangible projectile is comprised of a thermoset mixed with a powdered metal.

[0023] In one embodiment, the thermoset is PDCPD.

[0024] In one embodiment, the powdered metal is copper. In another embodiment, the powdered metal is tungsten.

Brief Description of the Drawings

[0025] Embodiments of the present disclosure will be presented with reference to the attached drawings in which:

[0026] FIG. 1 is a schematic diagram of a round of ammunition employing a frangible projectile, shown partly in cross-section; [0027] FIG. 2 is a process diagram showing steps for making a frangible projectile, in accordance with an embodiment of the present disclosure;

[0028] FIG. 3A is a side view of a mold assembly for making a frangible projectile, in accordance with an embodiment of the present disclosure; and

[0029] FIG. 3B is a side sectional view of the mold assembly of FIG. 3A taken at line A-A in FIG. 3A

Description of Embodiments

[0030] Embodiments of the present disclosure are presented below by way of example only and not limitation. In one embodiment, a process for making a frangible projectile is disclosed. In another embodiment, a fragile projectile made using the process is disclosed.

[0031] Directional terms such as “top,” “bottom,” “upwards,” “downwards,” “vertically,” and “laterally” are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any article is to be positioned during use, or to be mounted in an assembly or relative to an environment. The use of the word “a” or “an” when used herein in conjunction with the term “comprising” may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one” and “one or more than one.” Any element expressed in the singular form also encompasses its plural form. Any element expressed in the plural form also encompasses its singular form. The term “plurality” as used herein means more than one, for example, two or more, three or more, four or more, and the like.

[0032] In this disclosure, the terms “comprising”, “having”, “including”, and “containing”, and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, un-recited elements and/or method steps. The term “consisting essentially of’ when used herein in connection with a composition, use or method, denotes that additional elements, method steps or both additional elements and method steps may be present, but that these additions do not materially affect the manner in which the recited composition, method, or use functions. The term “consisting of’ when used herein in connection with a composition, use, or method, excludes the presence of additional elements and/or method steps.

[0033] FIG. 1 depicts a perspective view of a round of ammunition 100 partly in cross- section. The round 100 includes a case 110, sized to fit within the barrel of a gun or an artillery piece. The case 110 includes an open end 112, a closed end 114, and an interior.

[0034] A propellant substance 120 is disposed in the interior of the case 110. An ignition device, such as a primer 130 is arranged at the closed end of the case 110 and is configured for igniting the propellant substance 120.

[0035] A frangible projectile (or bullet) 140 is disposed at the open end of the case 110 such that when the primer 130 is activated, the propellant substance 120 causes the projectile 140 to be propelled away from the closed end 114, towards a target.

[0036] The frangible projectile 140 includes a thermoset mixed with a powdered metal. In one embodiment, the thermoset is Polydicyclopentadiene or PDCPD. The powdered metal is made of tungsten or copper. In some embodiments, the powdered metal is powdered tungsten while in other embodiments, the metal is powdered copper. In other embodiments one or more of tin, copper, zinc, and/or tungsten may be used to form the powdered metal.

[0037] PDCPD fluid has a lower viscosity than other thermosets and thermoplastics. Advantageously, PDCPD has a low porosity and does not accumulate air bubbles therein, which makes it a high density material desirable for bullet manufacturing as it leads to a high ballistic coefficient. The higher the ballistic coefficient, the better the material for the intended application.

[0038] Similarly, tungsten is an desirable choice for the powdered metal due to its high density which is over 19 g/cm ³ . Copper has a density of 8.96 g/cm ³ but is typically available at a lower cost than tungsten. Consequently copper can be used for making projectiles that are lighter and cheaper than their counterparts that may be made of tungsten. [0039] FIG. 2, depicts a flowchart summarizing a process 200 for making a frangible projectile in accordance with one exemplary embodiment of the present invention. At step 210 a predetermined amount of powdered metal is measured by weight. As noted above the powered metal may be one or more of powdered tungsten, powdered copper or any other suitable powdered metal or similar material .

[0040] At step 220, a predetermined amount of thermoset resin is measured by weight. These predetermined amounts of the powdered metal and thermoset are chosen depending on the desired rigidity of the frangible projectiles produced.

[0041] At step 230, the measured amounts of the thermoset resin and the powdered metal are mixed together to produce a slurry mixture. The mixing is done at room temperature under normal ambient conditions. The mixing may be done manually or using an agitator.

[0042] At step 240 the slurry mixture is poured into a mold . This process is described later and further illustrated in FIG. 3A and FIG. 3B.

[0043] At step 250, the slurry mixture is cured while in the mold. In one embodiment, the slurry mixture is cured under atmospheric conditions. In another embodiment, the slurry mixture is cured under pressure, such as in an autoclave. In yet another embodiment, the slurry mixture is cured in vacuum.

[0044] It has been found that curing under pressure yields the best results in reducing porosity. For example, when curing the slurry mixture under pressure in an autoclave very few bubbles formed in the resulting substance. In other words the resulting substance had a low porosity. Curing the slurry mixture under vacuum produced a substance of acceptable porosity but not as good as the one produced when curing the slurry mixture under pressure.

[0045] The above process 200 is not limited to making a frangible projectile to be used in a round of frangible ammunition. As would be appreciated by persons of skill in the art, any object having the desired properties of high density, low porosity, and yet the ability to be frangible when striking a hard target may be formed by the above-described process. [0046] FIG. 3A and FIG. 3B depict a mold 300 used to make frangible projectiles for use in rounds of frangible ammunition is shown. The mold 300 in the depicted embodiment includes three layers: the bottom mold 320, the top mold 330, and a three funnel block 340.

[0047] The bottom mold 320 and the top mold 330 are secured together by a plurality of screws 350. A bullet (or projectile) diffuser mold 310 is formed in bottom mold 320 and top mold 330. The diffuser mold is aligned with the funnels 345. The spring pings 380 keep the three funnel block 340 aligned with respect to the top mold 330 and the bottom mold 320 such that resin may be poured into the funnels 345 and end up in the diffuser mold.

[0048] An O-ring 390 is positioned around each of the diffuser molds 310 between top mold 330 and the bottom mold 320. The O-ring ensures a tight seal between the top mold 330 and bottom mold 320, such that the resin remains in the diffuser molds 310 until it cures.

[0049] During the process of making the frangible bullets, the slurry mixture of thermoset and powdered metal is poured into each of the funnels 345. The mold 330 is placed in an autoclave under pressure, placed in vacuum, or left at room temperature. Once the slurry mixture has cured, the three funnel block 340 is removed. The screws 350 can then be unfastened and the top mold 330 can be removed from the lower mold 320. The bullets may then be removed from the diffuser molds.

[0050] In accordance with another embodiment of the present invention, an ammunition round such as ammunition 100 is provided that includes a case such as case 110, a propellant substance such as propellant substance 120, an ignition device such as ignition device primer 130 and a frangible projectile such as frangible projectile 140. The case is sized to fit within the barrel of a gun or an artillery piece, the case having an open end, a closed end and an interior. The propellant substance 120 disposed in the interior of the case 110. The ignition device arranged at the closed end of the case and configured for igniting the propellant substance. The frangible projectile 140 disposed at the open end such that when the ignition device is activated, the propellant substance causes the projectile to be propelled away from the closed end. The frangible projectile is made of a thermoset mixed with a powdered metal. The frangible projectile 140 may be made using process 200 as described above.

[0051] Advantageously, the combination of PDCPD and a powdered metal such as tungsten, in the exemplary process 200 described above, results in a high density frangible projectile 140. The higher density translates to higher kinetic energy being applied to the target by the projectile upon impact, than the energy from another projectile of a similar size but lower density.

[0052] Additionally, the frangible projectiles made of PDCPD and powdered metal such as tungsten powder have better dispersion upon impact. Furthermore, materials such as tungsten are environmentally friendly whereas other metals such as lead are not environmentally friendly.

[0053] The above-described embodiments are intended to be examples of the present disclosure and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention, which is defined solely by the claims appended hereto.