Patent Application
20050188890
This invention relates to bullets and making bullets and, more particularly, to a composition for a frangible bullet and method of making the same.
Nearly all bullets used by civilians, as well as by the United States military, have a lead core. Lead is used for bullet cores because it has a high density. Lead cores produce increased accuracy and effectiveness when compared to many other types of bullets. Further, lead has a relatively low melting point. Therefore, it is inexpensive to form lead into the core of a bullet when compared with metals having a high melting point. In addition, lead is less expensive than other metals that may have a high density and a low melting point.
A shortcoming associated with bullets having lead cores is that, because lead usually comprises 90-95% of the total weight of bullets, bullets have the potential to introduce large quantities of lead into the environment. Bullets are often left in large quantities on the grounds of practice ranges and on battlefields. The lead leaches into the environment from whole or fragmented bullets that fall onto or are buried in the ground, eventually contaminating the soil, rain water run off and ground water. As a result, wildlife, and possibly even humans, may suffer lead poisoning from the contaminated ground water. Also, the predators of such wildlife suffer from secondary lead poisoning after ingesting the wildlife. In addition, when shooting ranges are converted into residential areas, human exposure to lead may lead to numerous health problems, especially for children exposed to lead. Such health problems include, for example, damage to the nervous system, increased blood pressure, and decreased fertility. Further, the lead may leach into water supplies, potentially harming all living things taking water from such a contaminated supply.
The cost of hazardous waste clean-up, such as lead clean-up, is often significant. Therefore, the operators of outdoor shooting ranges do not voluntarily engage in clean-up operations. Thus, lead contamination of the environment by bullets having lead cores left on such ranges continues to grow.
In view of the environmental hazards resulting from bullets having a lead core, it is desired to develop a bullet that eliminates or reduces these hazards. One solution to the environmental problems associated with lead is to design bullets that do not contain a lead core. However, when used for the purpose of desired injury to the target, non-lead core bullets are often less dense than bullets having a lead core. This lesser density results in inferior ballistic performance and may also result in less stopping power.
During the past several decades, bullet manufacturers have been experimenting with a variety of different types of bullet core and bullet jacket materials. One of the reasons for such experimentation is the desire to avoid the contamination issues associated with lead core bullets. Lead vapors and lead dust caused by the use of standard lead bullets in indoor shooting ranges are a significant hazard to employees and users of such ranges. As previously mentioned, the lead from standard bullets leaches into the soil, eventually contaminating the soil, rainwater run-off and ground water. One of the materials sometimes used, with or without lead, in the manufacture of bullet cores is zinc, for the presence of zinc can act like a battery anode and prevent the lead from reacting with the environment, thereby preventing environmental contamination of soil and water.
Cast or wrought zinc bullets using conventional zinc alloys have been made into bullets in solid core format. Zinc bullets of this type are harder than lead, and do not deform much on impact. As a result, such zinc bullets ricochet considerably more than lead bullets. The use of conventional zinc bullets at shooting ranges poses considerable capture problems, and represents a safety hazard due to the possibility that a ricocheted bullet could hit unintended targets (such as humans) near the intended target. These capture and safety issues have caused all major manufacturers of bullets to discontinue the manufacture of conventional solid core zinc bullets.
Alternatives to solid core zinc bullets have been developed. Typically, these alternative bullets involve fabrication of a core from discrete pieces of zinc. These pieces of zinc are, generally, in the form of stranded zinc wire pressure formed into a compact core within a copper jacket. Such fabrication is difficult to perform and involves the use of expensive stranded zinc wire.
Alternate materials, such as tungsten, have been used for bullet cores. However, tungsten is a very expensive material. Sintered iron cores have also been used, but the sintering operation is costly and difficult to control to a specific degree of core consolidation. Hence, variations in core tensile strengths results from such a process. These differing tensile strengths give rise to differing fragmentation performance of the bullet upon impact. Injection molded cores made from metal powder mixed with thermoplastic resin, such as nylon, have also been manufactured. These injection-molded cores require the use of sophisticated, expensive molding machinery.
In addition to problems of ricochet, when used at shooting ranges, bullets of the prior art do not always address other hazards to individuals, including over-penetration, and back-splatter. While penetration is desirable in a combat or hunting situation when it is desired to inflict harm on the intended target, when in target practice, penetration of the target leads to costly damage to target systems and training structures.
Thus, it is desired to provide a frangible bullet that does not have the ricochet, penetration, and back-splatter problems associated with conventional projectiles, that does not contribute to contamination of the environment or poisoning of persons or animals, and that is reasonable in the costs and other resources required for the composition and manufacture of the bullet.
As discussed above, most bullets have a lead core because the use of lead ensures that the bullet is accurate and powerful. Further, lead is relatively inexpensive, as is the cost of manufacturing bullets having a lead core due to the low melting point of lead. However, these lead bullets have the potential to introduce large quantities of toxic lead into the environment. Further, when used for situations where no harm is desired or required to the intended target, it is desired to product a projectile that does not penetrate, ricochet, or result in back-splatter.
The present invention comprises a composition and method for making a frangible bullet. The composition of the bullet according to the present invention is comprised primarily of zinc. In one embodiment, the bullet also comprises from about 0.5% to about 20%, by weight, of bismuth, tin, and/or indium. In yet another embodiment, the bullet also comprises one or more additives such as lead, iron, cadmium, aluminum, copper, and/or titanium.
A bullet made with the composition of the present invention is produced by: (a) admixing the zinc together with the bismuth, tin, and/or indium, and (b) forming the composition into the desired shape of the projectile. If the bullet is also to contain one or more of the aforementioned additives, those additives are included in the admixture before the bullet is formed. In one embodiment of the method according to the present invention, the forming process comprises hand casting, while in another embodiment, the forming process is die casting.
The present invention comprises a composition and method of making a frangible projectile, such as a bullet. In one embodiment, the composition comprises primarily zinc. The composition also comprises from about 0.5% to about 20%, by weight, of one or more of the combination of bismuth, tin, and/or indium.
In an exemplary embodiment of invention formed by hand casting, the composition comprises from about 1% to about 2% bismuth or tin added to zinc or to conventional zinc alloys. As an example, one composition comprises:
The “second additives” of lead, iron, cadmium, aluminum, copper, titanium, and zinc in this example comprise a conventional zinc alloy.
Bullets created according to the above exemplary composition were shot at rifle velocity at a conventional target. Upon impact with the target, these bullets disintegrated entirely. When these bullets were shot at velocities as low as typically achieved with a handgun (circa 1000 feet per second) into a 45-degree inclined hardened steel plate in an enclosed box, all bullets made according to this composition disintegrated into particles less than 5 gains (0.319 grams) in weight, satisfying the requirements of a frangible bullet.
During experimentation, compositions according to the present invention have been molded (formed) successfully into bullets using the process of hand casting and according to the die casting process. Generally, the method of making frangible projectiles according to the present invention comprises the step of admixing the composition, and forming a desired shape and size of the projectile. It is this forming step that involves hand casting or die casting.
When a bullet of the present invention is formed by the process of die casting, experiments have shown that a greater percentage of bismuth, tin, and/or indium may be desired to produce a frangible bullet of desired quality, including the lack of penetration, ricochet, and back-splatter. In one embodiment, the composition for bullets formed by the die casting process comprises from about 5% to about 20%, by weight, of bismuth, tin, and/or indium.
Various experiments were conducted with a wide range of tin, bismuth, and/or indium additives according to the present invention. Such experiments have demonstrated that as little as 0.5% by weight of tin, bismuth, tin and bismuth, or indium result in bullets of suitable frangibility. As much as 5% by weight of indium and as much as 20% by weight of tin, bismuth, or tin and bismuth have also resulted in frangible bullets.
It will be appreciated by those of skill in the art that the term “bullet” as used herein is not intended to be limited to any particular size or shape. Instead, the term “bullet” is intended to extend to all types of projectiles used in weaponry, including various types of ammunition used by small weapons, such as handguns, rifles, and semi-automatic and automatic guns, as well as mortars used by larger weapons.
It will also be appreciated that a projectile comprising the composition of the present invention may be made by processes well known in the art of metal working. It will be further appreciated that indium is generally an expensive material, particularly when compared to bismuth or tin. For this reason, a manufacturer may opt to include only bismuth and/or tin to create a frangible projectile according to the present invention.
It will be yet further appreciated that the projectile composition of the present invention contains primarily zinc, which is not poisonous to humans or wildlife. The composition is not required to contain any poisonous lead, and, if it does contain any lead (as in the example set forth herein), the level of lead is insignificant. If the composition contains no more than about 0.005% lead as in the above example, more than 200 such bullets are required to produce lead equal a single lead core bullet of the weight.
It will be still further appreciated that the materials and the processes used for production of projectiles of the composition according to the present invention are readily available and inexpensive, particularly when compared to many of the complex alternative bullets of the prior art. It will also be appreciated that the frangible bullet of the present invention significantly reduces the hazards of over-penetration, ricochet, and back-splatter.
The present invention can be further modified within the scope and spirit of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
