Improved geometry for polymer ammunition cartridges

Abstract

An improved polymer-based cartridge includes a primer insert defining a base end and connected to a cartridge body that extends forward to a shoulder region and has a length defined by industry standards for that caliber. A cartridge nose extends forward from the cartridge body and has an industry standard outer angle. An interference region, noncompliant with the industry standards, connects the industry standard angle to the neck. The interference region causes interference between the cartridge nose and a shoulder support surface defined by an industry compliant firearm chamber of the same caliber. The improved polymer cartridge thus exceeds maximum dimensions set by industry standards. A second interference region can be defined at the distal end of neck and is a result of an increase to the overall axial length of the cartridge in comparison to the corresponding length in an industry standard cartridge.

What is claimed is: 
     
         1 . A polymer-based ammunition cartridge for use in a firearm having a chamber with internal chamber dimensions that are compliant with dimensions set by industry standards, the cartridge comprising:
 a primer insert defining a base end;   a cartridge body connected to and extending from the primer insert to a shoulder region, wherein the cartridge body has an axial length that is compliant with the industry standard dimensions for a specified caliber of cartridge; and   a cartridge nose extending from the shoulder region and comprising a first angle specified by the industry standards for the specified caliber of cartridge, a neck, and an interference region formed between the first angle and the neck, the interference region being noncompliant with industry standards for the specified caliber of cartridge.   
     
     
         2 . The cartridge of  claim 1 , wherein the interference region is configured to cause interference between a shoulder, formed by the first angle, and a corresponding shoulder support surface formed in the industry standard firearm chamber for the specified caliber of cartridge. 
     
     
         3 . The cartridge of  claim 1 , wherein the interference region comprises a second angle that transitions the first angle into the neck. 
     
     
         4 . The cartridge of  claim 3 , wherein the second angle is between 15 to 25 degrees. 
     
     
         5 . The cartridge of  claim 3 , wherein the second angle is 20 degrees. 
     
     
         6 . The cartridge of  claim 1 , further comprising a second interference region formed at a distal end of the neck. 
     
     
         7 . The cartridge of  claim 6 , wherein the second interference region is configured to cause axial interference between the distal end of the neck and a chamber-bore interface in the industry standard firearm chamber for the specified caliber of cartridge. 
     
     
         8 . The cartridge of  claim 7 , wherein the second interference region comprises a 0.5% to 5% increase in overall axial cartridge length, defined from the base end to the distal end of the neck, beyond a corresponding industry standard axial cartridge length for the specified caliber of cartridge. 
     
     
         9 . The cartridge of  claim 8 , wherein the second interference region is a 2% increase to the overall axial cartridge length beyond the corresponding industry standard axial cartridge length for the specified caliber of cartridge. 
     
     
         10 . The cartridge of  claim 1 , wherein the interference region is configured as a 0.5 to 5% increase in axial length, defined from the base end to a proximal end of the neck, beyond a corresponding industry standard axial length for the specified caliber of cartridge. 
     
     
         11 . The cartridge of  claim 10 , wherein the interference region is a 2% increase in the axial length beyond the corresponding industry standard axial length for the specified caliber of cartridge. 
     
     
         12 . The cartridge of  claim 1 , further comprising a shoulder joint formed in the shoulder region, the shoulder joint configured to couple the cartridge body with the cartridge nose. 
     
     
         13 . The cartridge of  claim 1 , wherein the specified caliber of cartridge is a 308 Winchester cartridge. 
     
     
         14 . A method for making a nonstandard polymer ammunition cartridge for use in a firearm having internal chamber dimensions compliant with dimensions set by an industry standard for a specified caliber of cartridge, the method comprising:
 molding, over a primer insert that forms a base end, a polymer cartridge having a cartridge body and a cartridge nose, the cartridge body extending from the primer insert to a shoulder region, wherein cartridge body length from the base end to the shoulder region is compliant with industry standard dimensions for the specified caliber of cartridge;   the cartridge nose extending from the shoulder region and comprising a first angle compliant with the industry standards for the specified caliber of cartridge, a neck, and an interference region between the first angle and the neck, the interference region being noncompliant with industry standards for the specified caliber of cartridge.   
     
     
         15 . The method of  claim 14 , wherein the molding of the interference region is configured to cause interference between a shoulder of the cartridge nose and a corresponding shoulder support surface formed in the industry standard firearm chamber for the specified caliber of cartridge. 
     
     
         16 . The method of  claim 14 , wherein the molding of the interference region comprises molding a second angle that radially transitions the first angle into the neck. 
     
     
         17 . The method of  claim 16 , wherein molding the second angle comprises molding a 15 to 25 degree angle transitioning from the first angle to the neck. 
     
     
         18 . The method of  claim 14 , wherein the molding of the polymer cartridge further comprises molding a second interference region at a distal end of the neck, the second interference region configured to cause axial interference between the distal end of the neck and a chamber-bore interface in the industry standard firearm chamber. 
     
     
         19 . The method of  claim 18 , wherein molding of the second interference region comprises molding a 2% increase in overall axial length, defined from the base end to the distal end of the neck, beyond a corresponding industry standard overall axial length for the specified caliber of cartridge. 
     
     
         20 . The method of  claim 14 , wherein the molding of the polymer cartridge further comprises:
 first, molding the cartridge body over the primer insert, wherein the cartridge body has a shoulder coupling region opposite the overmolded primer insert; and   second, molding the cartridge nose to connect to the shoulder coupling region, wherein a lower end of the cartridge nose comprises a coupling joint configured to engage the shoulder coupling region.