Two-piece primer insert for polymer ammunition

A two piece primer insert for ammunition comprising:

• an upper primer insert portion connected to a lower primer insert portion at an insert joint, wherein the upper primer insert portion comprises
• an upper primer top surface,
• an upper primer insert bottom surface opposite the upper primer insert top surface,
• an upper primer flash hole aperture through the upper primer insert top surface and the upper primer bottom surface, and
• a substantially cylindrical coupling element extending away from the upper primer bottom surface,
• wherein the lower primer insert portion comprises:
• a lower primer bottom surface 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 flash hole aperture through the lower primer bottom surface, wherein the lower flash hole aperture is about the same diameter as the upper primer flash hole aperture;
• a middle flash hole groove in the bottom surface of the lower primer insert portion around the lower flash hole aperture, the middle flash hole groove is positioned between the upper primer flash hole aperture and the lower flash hole aperture and configured to receive a polymer overmolding, wherein the middle flash hole groove has a diameter greater than the lower flash hole aperture and the upper primer flash hole aperture.