US Patent 11788825 Polymer ammunition and cartridge having a convex primer insert

The present invention provides a primer insert for a polymer ammunition cartridge. The primer insert has a top surface opposite a bottom surface. The top surface has a primer recess defined therein, which is in fluid communication with the propellant chamber of the ammunition cartridge through a flash hole defined through the bottom surface. A groove is defined in the primer recess and surrounds the flash hole. A planar portion of the bottom surface surrounding the flash hole is connected to a vertical coupling element by a transition region. The transition region has a first and second concave portions positioned around a transition protrusion. An extraction flange is formed about the top surface.