The present invention provides a multi piece primer insert for ammunition comprising: an upper primer insert portion connected to a lower primer insert portion, wherein the upper primer insert portion comprises an upper primer bottom surface and an upper primer top surface opposite the upper primer bottom surface, an upper primer aperture through the upper primer bottom surface, a substantially cylindrical coupling element extending away from the upper primer bottom surface, wherein the lower primer insert comprises: a lower primer top surface opposite a lower primer bottom 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 extending to the primer recess; and a flash hole groove in the top surface of the upper primer insert portion, the flash hole groove extends circumferentially about the upper primer aperture and the flash hole groove is larger than the upper primer aperture, and wherein the flash hole groove is between the upper primer aperture and the lower flash hole aperture.