Medium caliber polymer ammunition cartridge

A medium caliber polymer-based ammunition cartridge, comprising:

• an insert having a top surface and a bottom surface, a coupling element extending from the top surface, a primer pocket formed through the bottom surface, and a flash hole in fluid communication with the primer pocket and extending through the top surface;
• a polymer body engaged to the insert forming an internal propellant chamber, wherein a first end of the polymer body is molded about the coupling element and into the flash hole and wherein a second end, opposite the first end, forms a nose joint;
• a polymer nose engaged to the nose joint of the polymer body, the polymer nose having a shoulder transitioning into a projectile opening, and an internal annular ridge having a proximal side and a distal side connected by a flat surface, wherein the annular ridge is configured to engage a cannelure defined in an outer surface of a projectile configured to be loaded into the projectile opening.

The cartridge of 37, wherein the one or more crush seals comprise at least one annular tip seal formed at a distal end of the polymer nose and at least one annular shoulder seal formed around an outer surface of the shoulder.