Annular ridged polymer-based ammunition cartridges

Abstract

A polymer cartridge includes an insert defining the base end and a body extending from the insert. The body forms a powder chamber which is in communication with a primer pocket formed in the insert via a flash hole formed through the insert top surface. A nose extends forward from the body and includes a shoulder that transitions into a neck defining a projectile aperture. An annular ridge is formed about the inner surface of the neck and positioned between the projectile aperture and the shoulder. The annular ridge is designed to engage the outer surface of a bullet that is the same caliber of the polymer cartridge. The bullet is designed with a groove corresponding to the location of the annular ridge so that the assembled cartridge is within the acceptable range for the total axial length thereof.

What is claimed is: 
     
         1 . A polymer-based ammunition cartridge, comprising:
 an insert forming a base end, the insert having a primer pocket defined through a bottom surface, a flash hole defined through an upper surface and in communication with the primer pocket, and a groove forming an extraction flange about an outer edge of the bottom surface;   a body extending from the insert to a forward end defining a powder chamber, wherein the flash hole fluidically connects the powder chamber to the primer pocket;   a nose extending from the body, the nose having a shoulder transitioning into a neck defining a projectile aperture; and   at least one annular ridge formed about an inner surface of the neck between the shoulder and the projectile aperture, the annular ridge configured to frictionally engage an outer surface of a projectile configured to be loaded in the projectile aperture.   
     
     
         2 . The cartridge of  claim 1 , wherein the annular ridge forms a seal between the neck and the projectile. 
     
     
         3 . The cartridge of  claim 1 , wherein the annular ridge is configured to engage a groove defined in the outer surface of the projectile. 
     
     
         4 . The cartridge of  claim 1 , wherein engagement of the annular ridge with the projectile is configured to generate a bullet pull force of at least 45 pounds per square inch. 
     
     
         5 . The cartridge of  claim 1 , wherein an inner diameter defined by the annular ridge is less than a maximum outer diameter of the projectile. 
     
     
         6 . The cartridge of  claim 1 , wherein the nose is integrally molded with the body. 
     
     
         7 . The cartridge of  claim 6 , wherein the body is molded over the insert. 
     
     
         8 . The cartridge of  claim 1 , further comprising a second annular ridge formed about the inner surface of the neck. 
     
     
         9 . The cartridge of  claim 8 , wherein the second annular ridge is formed between the projectile aperture and the annular ridge. 
     
     
         10 . The cartridge of  claim 9 , wherein the annular ridge and the second annular ridge are configured to engage two grooves defined in the outer surface of the projectile. 
     
     
         11 . The cartridge of  claim 10 , wherein engagement of the two grooves with the annular ridges is configured to concentrically align the projectile in the neck. 
     
     
         12 . The cartridge  claim 1 , wherein the annular ridge comprises a semi-spherical profile. 
     
     
         13 . The cartridge of  claim 1 , wherein the annular ridge comprises a rectangular profile. 
     
     
         14 . The cartridge of  claim 1 , wherein a total axial length of the cartridge plus the projectile loaded to a depth sufficient for engagement of the annular ridge with a cannelure is within an acceptable range of total axial length for a given caliber of the cartridge. 
     
     
         15 . A nose for a polymer-based ammunition cartridge, the nose comprising:
 a shoulder transitioning into a neck;   a shoulder joint opposite the neck;   a projectile aperture formed at a distal end of the neck; and   an annular ridge formed about an inner surface of the neck between the projectile aperture and the shoulder, the annular ridge configured to engage an outer surface of a projectile loaded into the cartridge.   
     
     
         16 . The nose of  claim 15 , further comprising a second annular ridge formed about the inner surface of the neck. 
     
     
         17 . The nose of  claim 16 , wherein the second annular ridge is formed between the projectile aperture and the annular ridge. 
     
     
         18 . The nose of  claim 15 , further comprising a cartridge body engaged to the nose about the shoulder joint and an insert engaged to a lower end of the cartridge body to form the cartridge. 
     
     
         19 . A bullet configured to engage a polymer-based ammunition cartridge, the bullet comprising:
 a body extending between a base end and a tip end, a forward end of the body tapering inwards to a longitudinal centerline to define an ogive extending to the tip end; and   an annular groove formed in an external surface of the body, wherein the annular groove is configured to engage an annular ridge formed about an inner surface a cartridge neck between a projectile opening and a shoulder.   
     
     
         20 . The bullet of  claim 19 , further comprising a second annular groove formed in the external surface of the body, wherein the annular groove and the second annular groove are configured to engage two annular ridges formed about the inner surface of the cartridge neck.