Frangible firearm projectiles, methods for forming the same, and firearm cartridges containing the same

Abstract

Frangible firearm projectiles, firearm cartridges containing the same, and methods for forming the same. The firearm projectiles are formed from compacted metal powders that may include an anti-sparking agent. The compacted metal powders may be or include a compacted mixture of metal powders that may include powders of one or more of iron, zinc, bismuth, copper, tungsten, nickel, boron, and/or alloys thereof, and/or oxides thereof. The compacted mixture may be heat treated for a time sufficient to form a plurality of discrete alloy domains within the compacted mixture. The frangible firearm projectile may be formed by a mechanism that includes vapor-phase diffusion bonding and oxidation of the metal powders and that does not include forming a liquid phase of any of the metal powders or utilizing a polymeric binder. The anti-sparking agent may include a borate, such as boric acid.

1 . A frangible firearm projectile, comprising:
 a frangible projectile body consisting essentially of compacted metal powders, wherein the compacted metal powders include one or more metal powders, and wherein the one or more metal powders include one or more of an iron powder, a zinc powder, a copper powder, a tungsten powder, a bismuth powder, a nickel powder, and a tin powder; and   wherein the frangible firearm projectile includes an anti-sparking agent configured to reduce a propensity for the frangible firearm projectile to produce sparks upon striking a target after being fired; and further wherein the anti-sparking agent includes at least one of boric acid, borax, a borate, metaboric acid, tetraboric acid, and boron trioxide.   
     
     
         2 . The frangible firearm projectile of  claim 1 , wherein the anti-sparking agent is interspersed within the interior of the frangible projectile body. 
     
     
         3 . The frangible firearm projectile of  claim 1 , wherein the anti-sparking agent forms at least a portion of a coating on an exterior of the frangible projectile body. 
     
     
         4 . The frangible firearm projectile of  claim 1 , wherein the anti-sparking agent forms 0.5-5 wt % of the frangible firearm projectile. 
     
     
         5 . The frangible firearm projectile of  claim 1 , wherein anti-sparking agent includes a mixture of two or more of the boric acid, the metaboric acid, the tetraboric acid, and the boron trioxide. 
     
     
         6 . The frangible firearm projectile of  claim 1 , wherein at least one of the metaboric acid, the tetraboric acid, and the boron trioxide is formed from thermal decomposition of the boric acid within the frangible projectile body. 
     
     
         7 . The frangible firearm projectile of  claim 1 , wherein the one or more metal powders in the compacted metal powders are bound together to form a plurality of discrete alloy domains in the frangible projectile body by chemical bonds that include chemical bonds resulting from oxidation bonding of the one or more metal powders, and chemical bonds resulting from vapor-phase diffusion bonding between the one or more metal powders. 
     
     
         8 . The frangible firearm projectile of  claim 1 , wherein the one or more metal powders in the compacted metal powders are bound together in the frangible projectile body by chemical bonds resulting from at least one of oxidation bonding of at least one metal powder of the one or more metal powders and the anti-sparking agent, chemical bonds resulting from vapor-phase diffusion bonding of the at least one metal powder into the anti-sparking agent to form a plurality of discrete alloy domains, and chemical bonds resulting from the vapor-phase diffusion bonding of the at least one metal powder into the anti-sparking agent and oxidation of the at least one metal powder to form a solid solution that includes a three-dimensional network of bonds between at least one oxidized metal powder and the anti-sparking agent. 
     
     
         9 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 50-95 wt % of the copper powder and 4-48 wt % of the iron powder. 
     
     
         10 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 10-48 wt % of the copper powder and 50-95 wt % of the iron powder. 
     
     
         11 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 50-85 wt % of the copper powder and 15-45 wt % of the zinc powder. 
     
     
         12 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 60-97 wt % of the tungsten powder and 20-40 wt % of the copper powder. 
     
     
         13 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 80-97 wt % of the tungsten powder and 2-15 wt % of the bismuth powder. 
     
     
         14 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 40-55 wt % of the iron powder, 20-45 wt % of the copper powder, and 5-30 wt % of the zinc powder. 
     
     
         15 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 3-35 wt % of the iron powder, 45-75 wt % of the copper powder, and 15-30 wt % of the zinc powder. 
     
     
         16 . The frangible firearm projectile of  claim 1 , wherein the compacted metal powders include 45-65 wt % of the tungsten powder, 24-48 wt % of the iron powder, and 3-14 wt % of the zinc powder. 
     
     
         17 . The frangible firearm projectile of clam  1 , wherein the compacted metal powders include 95-99.75 wt % copper powder and 0.25-4 wt % of the anti-sparking agent. 
     
     
         18 . The frangible firearm projectile of  claim 1 , wherein the frangible firearm projectile has a density of at least 6.5 grams per cubic centimeter, wherein the frangible firearm projectile has a weight and is configured to break entirely into small particulate when fired at a metal surface at close range from a firearm cartridge, and wherein the small particulate has a maximum particle weight of 5% of the weight of the frangible firearm projectile. 
     
     
         19 . A firearm cartridge, comprising:
 a casing that defines an internal volume;   a propellant disposed in the internal volume;   a primer disposed in the internal volume and configured to ignite the propellant; and   the frangible firearm projectile of  claim 1  at least partially received in the casing.   
     
     
         20 . A method for forming the frangible firearm projectile of  claim 1 , the method comprising:
 preparing a mixture of metal powders and the anti-sparking agent;   compacting the mixture of metal powders and the anti-sparking agent to form a compacted mixture;   heating the compacted mixture to a heating set point temperature; wherein the heating set point temperature is at least 260° C. (500° F.) and less than 415.6° C. (780° F.);   maintaining the compacted mixture at a maintaining temperature for a maintaining time; wherein the maintaining time is at least 20 minutes, wherein the maintaining temperature is within 10% of the heating set point temperature; wherein the heating and the maintaining create a plurality of discrete alloy domains of the one or more metal powders within the compacted mixture; and   cooling the frangible firearm projectile.   
     
     
         21 . The method of  claim 20 , further comprising assembling a firearm cartridge containing the frangible firearm projectile.