Three-piece primer insert having an internal diffuser for polymer ammunition

A three piece primer insert for use in polymer ammunition comprising:

• an upper primer insert portion comprising an upper primer bottom surface, an upper primer aperture through the upper primer bottom surface, a groove positioned in the upper primer bottom surface around the upper primer aperture, wherein the groove is adapted to receive a polymer overmolding and a substantially cylindrical coupling element extending away from an upper primer top surface which is opposite the upper primer bottom surface;
• 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 larger 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 larger than the middle primer aperture.