Polymer ammunition cartridge having a three-piece primer insert

A polymeric ammunition cartridge comprising:

• a three piece primer insert comprising:
• an upper primer insert portion comprising an upper primer bottom surface, an upper primer aperture through the upper primer bottom surface, and a substantially cylindrical coupling element extending away from an upper primer top surface;
• a groove formed by the difference in diameter between the upper primer aperture and a middle primer aperture, wherein the groove is adapted to receive a polymer overmolding;
• a middle primer insert portion comprising a middle aperture and an upper joint of the middle primer insert portion positioned in contact with the upper primer bottom surface and adjacent to the groove, wherein the middle aperture is smaller than the upper primer aperture;
• and a lower primer insert portion in contact with the middle primer insert portion comprising a lower primer bottom surface in contact with a lower joint of the middle primer insert portion and opposite a lower primer top surface, a primer recess in the lower primer top surface that extends toward the lower primer bottom surface and adapted to fit a primer, a lower aperture through the lower primer bottom surface, wherein the lower aperture is smaller than the middle aperture;
• a substantially cylindrical polymeric middle body extending about the three piece 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 into the groove;
• 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.