Ammunition and explosives – Projectiles – Fragmenting
Reexamination Certificate
1999-01-07
2004-02-17
Tudor, Harold J. (Department: 3641)
Ammunition and explosives
Projectiles
Fragmenting
C102S517000, C102S529000, C086S054000, C075S246000, C416S066000
Reexamination Certificate
active
06691623
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a frangible projectile comprising cold compacted iron particles and, more specifically, to a frangible bullet for use in target and training applications.
There is a need for training ammunition that can reduce or eliminate the risk of ricochet. Frangible ammunition, which breaks into small pieces upon impact, has been used in the past to meet these needs. A frangible projectile disintegrates upon impact with no appreciable back splatter or ricochet which might injure the shooter, other persons nearby or equipment. Prior frangible projectiles have been made substantially of lead. The use of lead produces undesirable health risks from airborne and sedentary lead particles. Lead particles present a health risk to shooters and others nearby, as well as creating an environmental problem where the lead particles fall to the ground upon disintegration of the projectile.
One solution to the need for frangible, lead-free projectiles has been the use of a compacted, unsintered admixture of metal particles comprising tungsten and at least one other metal selected from the group of iron and copper, as disclosed in copending U.S. patent application Ser. No. 08/755,963, entitled “Lead-Free Frangible Projectile.” However, the admixture process and the use of tungsten adds to the cost of manufacturing such projectiles.
SUMMARY OF THE INVENTION
The projectiles of the present invention satisfy the need for lead-free frangible projectiles without the expense of high cost materials and processing. The projectiles of the present invention produce a similar “feel” and mimic the ballistic properties of lead projectiles of similar caliber and size. The projectiles of the present invention are unsintered. This deviates from existing powder metal technology where the projectiles are generally sintered to increase the strength, hardness, structural integrity and other mechanical properties. By using cold compaction without sintering, the projectiles are characterized by more complete frangibility upon impact with target media. A frangible projectile is defined herein as one designed to readily break-up upon impact with a hard surface in order to minimize ricochet or spatter.
Specifically, the present invention provides a frangible projectile comprising cold compacted iron powder. In a preferred embodiment, the projectile has a jacket of metal or polymer, with copper being the most preferred jacket material.
DETAILED DESCRIPTION OF THE INVENTION
The projectiles of the present invention will be more fully understood by reference to the following description. Both the projectiles and a process for the manufacture of the projectiles will be described. Variations and modifications of both the projectiles and the process can be substituted without departing from the principles of the invention, as will be evident to those skilled in the art.
The projectiles of the present invention are comprised of cold compacted iron powder. Cold compaction is used in its customary meaning, that is, that the compaction is carried out at substantially ambient conditions, without applied heat.
In order to provide particularly good frangibility, it is preferable that the iron particles used have a specific particle size distribution prior to being cold compacted. It has been found to be particularly advantageous to have a pre-compaction particle size distribution of about from 15 to 25% by weight of particles up to about 44 &mgr;m, about from 5 to 70% by weight of particles having a particle size of about from 44 to 149 &mgr;m, and about from 5 to 15% by weight of particles having a particle size of about from 149 to 250 &mgr;m. Even more advantageous is a pre-compaction particle size distribution of about 22% by weight of particles up to about 44 &mgr;m, about 68% by weight of particles having a particle size of about from 44 to 149 &mgr;m, and about 10% by weight of particles having a particle size of about from 149 to 250 &mgr;m. The desired particle size distribution can be obtained through a variety of conventional methods, including optical measurements and sifting. The particles are also available commercially in specific particle size distributions. A representative product is commercially available as Anchorsteel 1000 B, from Hoeganes Corp.
The particle size distributions described above have been found to provide the advantage of integrity of the projectile before and during firing and frangibility upon impact with a target media. While the relationship between particle size distribution and frangibility are not fully understood, it is believed to be a function of the mechanical interlocking of the particles after the cold compaction of the iron powder.
The projectiles of the present invention are preferably provided with a jacket. The jacket material can be selected from those customarily used in the art, for example, metal or polymeric material. Metals which can be used include aluminum, copper and zinc, with copper being a preferred choice. Polymeric materials which can be used include polyethylene and polycarbonate, with a low density polyethylene material being preferred.
The projectiles of the present invention can have a variety of configurations, including shot and bullets, but are preferably formed into bullets for use with firearms. The bullets can have noses of various profiles, including round nose, soft nose, or hollow point. Either the bullet or the jacket, if so provided, can include a driving band which increases the accuracy and reduces the dispersion of the bullet.
The projectiles of the present invention can be manufactured by a process wherein the powdered iron of the desired particle sizes are admixed to provide a mixture with the desired particle size distribution. The powdered iron can also preferably be mixed with a lubricant. This lubricant aids in removing the projectiles from the mold after compaction is complete. If a lubricant is to be added, it can be added to the powdered iron admixture. A preferred lubricant is zinc stearate. Up to about 1.0% by weight of zinc stearate can be beneficially added to the powdered iron prior to compaction. About 0.5% has been found to be particularly satisfactory.
The admixture is then placed in a die which is designed to provide the desired shape of the projectile. A wide variety of projectiles can be made according to the present invention, including shot and bullets. The invention is particularly beneficial in bullet manufacture, and especially those having a generally elongated configuration in which a leading end has a smaller circumference than a trailing end.
According to the present invention, the admixture of iron powder is cold compacted at a pressure of about from 50,000 to 120,000 psi, with a pressure of about 100,000 psi being particularly preferred. Compacting at a pressure of about 100,000 psi provides the best combination of projectile integrity before and during firing and frangibility upon impact with a target. The compaction step can be performed on any mechanical press capable of providing at least about 50,000 psi pressure for a dwell time which can be infinitesimally small. Presently available machinery operates with dwell times of about from 0.05 to 1.5 seconds. Preferably, a conventional rotary dial press is used.
After the projectile is formed by cold compaction, a jacket can be formed around the projectile if so desired. Such a jacket is preferred for a number of reasons. The jacket isolates the powdered iron material of the projectile from the gun barrel, preventing erosion of the rifling of the gun barrel which might result from direct contact between the interior surface of the barrel and the powdered iron of the projectile. The jacket also helps provide additional integrity of the projectile before and during firing as well as improving the ballistics of the projectile upon firing.
In the case of metal jackets, the jacket can be applied by any number of conventional processes, including acid or cyanide electroplating, mechanical swaging, spray coating, and chemical adhesiv
Huntley & Associates LLC.
RA Brands, LLC
Tudor Harold J.
LandOfFree
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