Method of Manufacturing a Polymer Jacketed Bullet
A method of producing a bullet with a polymer bullet jacket. The method of manufacture is accomplished by an injection operation that injects a molten plastic jacket around a suspended metal core in a simple and certain process.
U.S. Provisional Application for Patent No. 62/016,353, filed Jun. 24, 2014, with title “Polymer Jacketed Bullet and Method of Manufacturing” which is hereby incorporated by reference, Applicant claims priority pursuant to 35 U.S.C. Par. 119(e)(i).
Statement as to rights to inventions made under federally sponsored research and development
Not Applicable.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention related generally to bullets/projectiles (herein after referred to as bullets), and more particularly to a method of manufacturing polymer jacketed bullets.
2. Brief Description of Prior Art
It is well known in the industry to manufacture bullets and corresponding cartridge cases of either brass or steel. Typically, industry design standards call for materials that are strong enough to withstand extreme operating pressures and which can be formed into a cartridge case to hold the bullet, while simultaneously resist rupturing in the firing process.
Bullets are typically made of metal with hunting bullets being formed of a lead body or core with or without jacketing by another metal as for example, a copper jacket. Military ammunition will typically use steel jacketed bullets, which are erosive.
In all events, the friction between the bullets traveling through the barrel and the barrel itself causes wear on the interior of the barrel which shortens its life and, at some point in time will begin to interfere with the accuracy of the firearm. Furthermore, barrel fouling frequently occurs from metal scraped from the surface of the bullet or the jacket as a result of the friction. Prolonged firing of the firearm without cleaning can result in a loss of accuracy when the barrel is fouled.
A conventional bullet jacket is produced from gilding metal or commercial bronze by deep drawing. A sheet of the metal is blanked, cupped, and annealed. After annealing, the cup is then pickled in acid, washed and drawn into the final form. The jacket is then trimmed prior to being filled with lead. Another technology used to produce jacketed bullets is electroplating, whereby a swagged lead bullet may be copper plated with an extremely heavy layer of copper. This process is slow and expensive because the electroplating of individual parts is more difficult to control.
It is also known in the art to coat a bullet jacket in a low friction material such as molybdenum disulfide, nylon, polyurethane or polytetrafluoroethylene, for example. Such coatings however have been applied to the bullet jacket after the bullet is cast or swagged.
Regardless of the method used, in order for a bullet to achieve optimum terminal performance, its jacket and core must penetrate a target as a single unit and remain connected throughout the course of travel, regardless of the resistance offered by the target material.
Therefore, there is a need for an improved method of manufacturing a jacketed bullet over the prior art that is simple and cost effective to manufacture, and has sufficient durability to supplement or replace the conventional copper/zinc jacketing layer. The method of manufacture in the present invention is accomplished by a less complex plastic injection operation that injects a molten plastic jacket around a suspended metal core in a simple and certain process.
As will be seen from the subsequent description, the preferred embodiments of the present invention overcome disadvantages of the prior art. In this regard, the present invention discloses a process of suspending a projectile core in a plastic injection mold in order to inject a molten plastic jacket around the suspended metal core for the purpose of replacing the commonly used copper/zinc alloys. Still other objects will become apparent from the more detailed description which follows.
SUMMARY OF THE INVENTIONIn general, the present invention discloses a method of producing a bullet with a polymer bullet jacket. The method of manufacture is accomplished by an injection operation that injects a molten plastic jacket around a suspended metal core in a simple and certain process.
The core of the projectile is preferably made of a dense, malleably material, such as lead or a lead alloy, however the core could also be made of a non-lead material, malleable metal.
In manufacture, the core of the projectile is positioned within the mold such that the core is suspended within the cavity of the mold so that the surface of the core is not in contact with the interior surface of the mold. The positioning of the core may further be aided with at least one alignment pin.
After the core has been properly aligned, a thermal-plastic material is injected into the cavity via injection port. The injected material may entirely encapsulate the core, or alternatively, need only cover a portion of the core.
During the injection process, it is important to ensure that bonding incurs between the core and the injected material. One way to insure that adequate bonding is achieved is to heat the plastic material as hot as the material characteristics will allow, and to inject the material as quickly as possible. This allows the core to be heated by, and thereafter bonded to, the injected material.
The present invention is directed to polymer jacketed bullets, and method of manufacturing the same. The preferred method of manufacture incorporates a plastic injection operation that injects a molten plastic jacket around a suspended metal core that eliminates a number of the steps required in the prior art. The present application further discloses a projectile having a metal core surrounded by a plastic jacket made from a flexible, resilient material that will reduce friction between the bullet traveling through the barrel and the barrel itself. As will be described, the polymer jacketed bullet and method of manufacturing as disclosed further consists of components configured and correlated with respect to each other so as to attain the desired objective.
As is known, the core of the projectile is preferably made of a dense, malleably material, such as lead or a lead alloy, however in the present invention, the core could also be made of a non-lead material, such as bismuth, bismuth alloys, tungsten, tungsten alloys, tin or tin alloys, or any other dense, malleable metal that as will be described, will bond to the jacket. The bullets of the present invention are manufactured by an injection molding process from a composite polymer by feeding the polymer through an injection molding apparatus. The properties of the selected polymer material provide several advantages over the conventional brass and lead materials commonly used for cartridge cases and bullets, respectively. For example, the polymer material provides a way for the jacket to hold the bullet that replaces the prior art step of crimping and eliminates a need to use adhesives in cases where adhesives are required to provide the proper bullet pull properties when using brass cases. Further, brass cartridge cases tend to form to the chamber was of the firearm when fired. In contrast, the composite polymer jacket of the present invention flexes during firing, but the material memory returns the jacket to its original dimensions.
In application, the core 12 of the projectile is positioned within a cavity 15 of a mold 20. Referring to
After the core 12 has been properly aligned within the bottom portion 22 of the mold 20, the top portion 23 is aligned with the bottom portion 22. When the bottom and top portions of the mold 20 fixture have been aligned, a press may be utilized to maintain the alignment during the high-pressure injection procedure.
A thermal-plastic material (not shown) is heated to at least the melting temperature, or preferably slightly above the melting temperature of the material, and is injected into cavity 15 via injection port 30. As illustrated, the core 12 has a front end 13 and a body 14. The injected material may entirely encapsulate the core 12, or alternatively, need only cover a portion of the core, preferably the body portion 14.
During the injection process, it is important to ensure that bonding incurs between the core 12 and the injected material, One way to insure that adequate bonding is achieved is to heat the plastic material as hot as the material characteristics will allow, and to inject the material as quickly as possible. This allows the core 12 to be heated by, and thereafter bonded to, the injected material.
It should be understood with the present process, the jacket of the projectile is now made from a flexible, resilient material such as polytetrafluoroethylene so that the jacket takes most or essentially all of the deformation of the projectile and barrel when the projectile is fired. The jacket of the projectile thus protects the lead or ceramic core from deformation or damage and reduces wear on the barrel. In addition, when the projectile leaves the barrel, the ridges on the projectile formed by the rifling grooves of the barrel either reduce in size or disappear altogether. The projectile consequently has a smoother, more aerodynamically efficient surface during flight and has a more accurately predictable flight path.
It should be further understood the present invention is not limited to a particular-described caliber and is intended to be applicable to other calibers as well.
Several benefits therefore occur as a result of using bullets coated according to the invention. For one, there is a dramatic reduction in barrel fouling from surface metal of the bullets, particularly surface metal from the jackets of bullets. The clearly reduced friction during bullet travel through the barrel reduces wear on the barrel and thereby lengthens the useful life of the barrel.
Because of the increased slipperiness of the bullets due to the reduced friction, peak pressures present in the barrel during the firing of the firearm are reduced which in turn allows a given firearm to fire cartridges loaded to achieve higher velocities, all the while maintaining safe pressures.
Bullets made according to the method of the present invention may be fired with enhanced accuracy as a result of reduced variances in friction during firing. It also appears that the reduction in friction serves to dampen vibration of the barrel as the bullet travels through it, further enhancing accuracy.
Because of the lack of fouling, the firearms do not require cleaning as frequently.
It is expected that there will be an improvement in long range ballistics as a result of smoother airflow about the bullet due to the improved lubricity of its surface.
It is also expected that there will be improved penetration into a target, particularly when using hunting bullets, due to the increase lubricity of the bullet surface.
In repeating firearms, particularly semi-automatic firearms, improved reliability in feeding and chambering is to be expected again, due to the high lubricity of the surface of the bullet. It is expected that there will be a lesser loss of accuracy for sustained firing of a firearm due to slower temperature rise of the barrel. In particular, because there will be less friction using bullets made according to the present invention, less heat due to friction will be generated and the temperature rise rate of the barrel will be slower.
Lastly, but certainly not least, the manufacturing process as described herein, is cost effective in both labor hours and material. As disclosed, plastic material is replacing the more costly copper and zinc commonly used for making bullet jackets in the prior art. Further, a number of steps required in the prior art manufacturing process are now eliminated. It will therefore be appreciated that bullets made according to the invention and method of invention possess substantial advantages over those heretofore known.
Although the above description contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. As such, it is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the claims.
It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention. Thus the scope of the invention should be determined by the appended claims in the formal application and their legal equivalents, rather than by the examples given.
Claims
1. A method of manufacturing a bullet comprising the steps of:
- positioning a core within a cavity of a mold such that the core is suspended within said cavity so that the entire outer periphery of the core is not in contact with an interior surface of said cavity, supporting said core within said cavity with at least one alignment pin,
- injecting a thermoplastic material into said cavity via an injection port such that the injected material covers a portion of the core.
2. The method as recited in claim 1, including the step of heating the thermoplastic material above a melting temperature of the thermoplastic material, and then performing the injecting step as quickly as possible.
3. The method as recited in claim 2, wherein in the injecting step, the injected material only covers a body portion of the core.
4. The method as recited in claim 3, wherein in the injecting step, the injected material does not cover a front end of the core.
5. A method of manufacturing a bullet comprising the steps of positioning a core within a cavity of a mold such that a spacing is disposed between an entire outer periphery of an outer surface of said core and an interior wall of said cavity; and injecting a thermoplastic material into said cavity such that said injected material covers a body portion of said core, and wherein a front end portion of said core is not covered with said injected material.
6. The method of claim 5, wherein said core is positioned in said cavity using at least one alignment pin.
Type: Application
Filed: Jun 24, 2015
Publication Date: Dec 29, 2016
Inventor: Michael A. Winge (Boonville, IN)
Application Number: 14/748,929
