Subsonic small-caliber ammunition and bullet used in same

Abstract

A bullet for use with a small caliber rifle comprises a jacket and a lead core provided within the jacket. The jacket is drawn from a copper alloy material. A bearing surface portion of the jacket has a nominal thickness less than about .010″ and the copper alloy material of at least the bearing surface portion of the jacket has a nominal hardness that is substantially greater than an as-drawn hardness of the copper alloy material of the bearing surface portion of the jacket.

1 . A bullet for use with a small caliber rifle, comprising:
 a jacket drawn from a copper alloy material, wherein a bearing surface portion of the jacket has a nominal thickness less than about 0.010″ and wherein the copper alloy material of at least the bearing surface portion of the jacket has a nominal hardness that is substantially greater than an as-drawn hardness of the copper alloy material of the bearing surface portion of the jacket; and   a lead core provided within the jacket.   
     
     
         2 . The bullet of  claim 1  wherein the bearing surface portion of the jacket is at least partially coated with a friction-reducing material composition. 
     
     
         3 . The bullet of  claim 2  wherein the friction-reducing material composition is molybdenum disulfide. 
     
     
         4 . The bullet of  claim 3  wherein the bearing surface portion is coated in its entirety with the friction-reducing material composition. 
     
     
         5 . The bullet of  claim 1  wherein the nominal hardness of the copper alloy material of at least bearing surface portion corresponds to a tensile strength of between about 32 ksi and about 44 ksi. 
     
     
         6 . The bullet of  claim 5  wherein the bearing surface portion of the jacket is at least partially coated with a friction-reducing material composition. 
     
     
         7 . The bullet of  claim 6  wherein the friction-reducing material composition is molybdenum disulfide. 
     
     
         8 . The bullet of  claim 7  wherein the bearing surface portion is coated in its entirety with the friction-reducing material composition. 
     
     
         9 . The bullet of  claim 5  wherein the bearing surface portion of the jacket has a thickness between about 0.004″ and about 0.008″. 
     
     
         10 . The bullet of  claim 1  wherein the bearing surface portion of the jacket has a thickness between about 0.004″ and about 0.008″. 
     
     
         11 . A round of ammunition configured for providing sufficient energy for cycling a bolt carrier in a rifle having a gas-energized bolt carrier actuation mechanism, comprising:
 a small-caliber cartridge casing configured in accordance with an original equipment manufacturer (OEM) specification for the rifle;   a bullet having a bearing surface portion thereof engaged within a bullet receiving opening of the small-caliber cartridge casing thereby forming a propellant-receiving cavity within the small-caliber cartridge casing, wherein the bullet has a core made of a metal having lead as its major constituent component and a jacket drawn from metal having copper as its major constituent component, wherein a nominal thickness of the jacket is less than about 0.010″, and wherein at least the bearing surface portion of the jacket has a nominal hardness that is substantially greater than an as-drawn hardness of the jacket; and   a propellant within the propellant-receiving cavity of the small-caliber cartridge casing, wherein the propellant is configured by a manufacturer thereof for being used in medium caliber ammunition.   
     
     
         12 . The round of ammunition of  claim 11  wherein the bearing surface portion of the jacket is at least partially coated with a friction-reducing material composition 
     
     
         13 . The round of ammunition of  claim 12  wherein the friction-reducing material composition is molybdenum disulfide. 
     
     
         14 . The round of ammunition of  claim 13  wherein the bearing surface portion is coated in its entirety with the friction-reducing material composition. 
     
     
         15 . The round of ammunition of  claim 11  wherein the nominal hardness of said jacket metal of at least the bearing surface portion corresponds to a tensile strength of between about 32 ksi and about 44 ksi. 
     
     
         16 . The round of ammunition of  claim 15  wherein the bearing surface portion of the jacket is at least partially coated with a friction-reducing material composition. 
     
     
         17 . The round of ammunition of  claim 16  wherein the friction-reducing material composition is molybdenum disulfide. 
     
     
         18 . The round of ammunition of  claim 17  wherein the bearing surface portion is coated in its entirety with the friction-reducing material composition. 
     
     
         19 . The round of ammunition of  claim 15  wherein the bearing surface portion of the jacket has a thickness between about 0.004″ and about 0.008″. 
     
     
         20 . The round of ammunition of  claim 11  wherein the bearing surface portion of the jacket has a thickness between about 0.004″ and about 0.008″. 
     
     
         21 . A method for making a bullet for use with a small caliber rifle, comprising:
 providing a jacket having a thickness less than about 0.010″, wherein the jacket is drawn from a copper alloy material;   forming a lead core within a core-receiving cavity of the jacket; and   hardening at least a bearing surface portion of the jacket to have a nominal hardness that is substantially greater than an as-drawn hardness of the jacket after forming the lead core within the core-receiving cavity of the jacket.   
     
     
         22 . The method of  claim 21  wherein said hardening includes shot peening the jacket with steel shot. 
     
     
         23 . The method of  claim 22 , further comprising:
 exposing the jacket and the steel shot to a friction-reducing material composition during said shot peening such that said shot peening causes at least a portion of an exterior surface of the jacket to become coated with a layer of the friction-reducing material composition.   
     
     
         24 . The method of  claim 23  wherein the friction-reducing material composition is molybdenum disulfide. 
     
     
         25 . The method of  claim 21  wherein the nominal hardness of the copper alloy material of at least the bearing surface portion corresponds to a tensile strength of between about 32 ksi and about 44 ksi after performing said hardening. 
     
     
         26 . The method of  claim 25  wherein said hardening includes shot peening the jacket with steel shot. 
     
     
         27 . The method of  claim 26 , further comprising:
 exposing the jacket and the steel shot to a friction-reducing material composition during said shot peening such that said shot peening causes at least a portion of an exterior surface of the jacket to become coated with a layer of the friction-reducing material composition.