Lightweight polymer ammunition cartridge casings

A polymeric ammunition cartridge comprising:

• a substantially cylindrical primer 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 aperture 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;
• a substantially cylindrical polymeric middle body extending about the substantially cylindrical primer insert, wherein the substantially cylindrical polymeric middle body comprises:
• a substantially cylindrical polymeric bullet-end coupling element at a first end of the substantially cylindrical polymeric middle body opposite 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 aperture;
• and
• a substantially cylindrical polymeric bullet-end upper portion comprising a bullet-end coupling element connected to the substantially cylindrical polymeric bullet-end coupling element opposite a projectile aperture adapted to engage a bullet.