Lightweight polymer ammunition cartridge casings

Abstract

One embodiment of the present invention provides a polymeric ammunition cartridge and methods of making and using the same. The cartridge includes a substantially cylindrical insert connected to a substantially cylindrical polymeric middle body. The substantially cylindrical insert includes a top surface opposite a bottom surface and a substantially cylindrical coupling element that extends from the bottom surface, a primer recess in the top surface that extends toward the bottom surface, a primer flash hole positioned in the primer recess to extend through the bottom surface, and a flange that extends circumferentially about an outer edge of the top surface. The substantially cylindrical polymeric middle body includes a substantially cylindrical polymeric bullet-end and a substantially cylindrical polymeric coupling end connected by a powder chamber, wherein the substantially cylindrical polymeric coupling end extends over the substantially cylindrical coupling element and covers a circumferential surface of the primer flash hole.

What is claimed is: 
     
         1 . A method of making a substantially cylindrical insert by metal injection molding comprising the steps of:
 providing a mold of the substantially cylindrical insert to form a substantially cylindrical insert mold;   providing a feedstock comprising a powdered metal and a first binding agent and a second binding agent;   injection molding the feedstock into the substantially cylindrical insert mold to form an substantially cylindrical insert having a first size;   debinding the substantially cylindrical insert to remove the first binding agent; and   sintering the substantially cylindrical insert to remove the second binding agent and form a finished substantially cylindrical insert having a second size.   
     
     
         2 . The substantially cylindrical insert of  claim 1 , wherein the substantially cylindrical insert comprising a top surface opposite a bottom surface and a substantially cylindrical coupling element that extends from the bottom surface, a primer recess in the top surface that extends toward the bottom surface, a primer flash hole positioned in the primer recess to extend through the bottom surface, and a flange that extends circumferentially about an outer edge of the top surface. 
     
     
         3 . The substantially cylindrical insert of  claim 1 , wherein the powdered metal comprises stainless steel, brass, ceramic alloys. 
     
     
         4 . The substantially cylindrical insert of  claim 1 , wherein the powdered metal comprises 102, 174, 201, 202, 300, 302, 303, 304, 308, 309, 316, 316L, 316Ti, 321, 405, 408, 409, 410, 415, 416, 416R, 420, 430, 439, 440, 446 or 601-665 grade stainless steel. 
     
     
         5 . The substantially cylindrical insert of  claim 1 , wherein the substantially cylindrical insert further comprises a flange that extends circumferentially about an outer edge of the top surface; and
 a diffuser positioned in the primer recess comprising a diffuser flash hole aligned with the primer flash hole.   
     
     
         6 . The substantially cylindrical insert of  claim 1 , wherein the second size is about 10 percent to about 20 percent smaller than the first size. 
     
     
         7 . An ammunition cartridge comprising:
 a substantially cylindrical insert made by the process comprising providing a mold of the substantially cylindrical insert to form a substantially cylindrical insert mold; providing a feedstock comprising a powdered metal and a first binding agent and a second binding agent; injection molding the feedstock into the substantially cylindrical insert mold to form an substantially cylindrical insert having a first size; debinding the substantially cylindrical insert to remove the first binding agent; and sintering the substantially cylindrical insert to remove the second binding agent and form a finished substantially cylindrical insert having a second size; and bonded to a substantially cylindrical polymeric middle body comprising a substantially cylindrical polymeric bullet-end and a substantially cylindrical polymeric coupling end connected by a powder chamber, wherein the substantially cylindrical polymeric coupling end extends over the substantially cylindrical coupling element and covers an circumferential surface of the primer flash hole.   
     
     
         8 . The ammunition cartridge of  claim 8 , wherein the substantially cylindrical polymeric middle body comprise a nylon polymer. 
     
     
         9 . The ammunition cartridge of  claim 8 , wherein the substantially cylindrical insert is adhesively fitted to the substantially cylindrical polymeric middle body. 
     
     
         10 . The ammunition cartridge of  claim 8 , wherein the substantially cylindrical insert is adhesively fitted to the substantially cylindrical polymeric middle body with a curable polymer adhesive. 
     
     
         11 . The ammunition cartridge of  claim 8 , wherein the substantially cylindrical insert, the substantially cylindrical polymeric middle body or both comprises a coating to adjust the shrinkage. 
     
     
         12 . The ammunition cartridge of  claim 8 , wherein the substantially cylindrical polymeric bullet-end comprises a forward opening end having a first and a second mechanical interlock for engagement between the forward opening end and a bullet. 
     
     
         13 . The ammunition cartridge of  claim 8 , wherein the forward opening end comprises one or more cannelures formed on an outer circumferential surface of the forward opening end. 
     
     
         14 . The ammunition cartridge of  claim 8 , wherein the forward opening end comprises one, two, three, or more annular rings that mate with one, two, three, or more corresponding annular grooves positioned on the bullet. 
     
     
         15 . The ammunition cartridge of  claim 8 , wherein the forward opening end is crimped so that a polymeric material flows into an annular groove of a bullet. 
     
     
         16 . The ammunition cartridge of  claim 8 , wherein a bullet is adhesively fitted to the forward opening end. 
     
     
         17 . The ammunition cartridge of  claim 8 , further comprising a diffuser positioned in the primer recess comprising a diffuser flash hole aligned with the primer flash hole. 
     
     
         18 . A substantially cylindrical insert mold for making a substantially cylindrical insert by metal injection molding comprising:
 a top surface opposite a bottom surface and a substantially cylindrical coupling element that extends from the bottom surface;   a primer recess in the top surface that extends toward the bottom surface;   a primer flash hole positioned in the primer recess to extend through the bottom surface; and
 a flange that extends circumferentially about an outer edge of the top surface.