The
flash hole is the part of a
cartridge that is the circular opening at the bottom of the case and is where the
primer jets out the
flame and hot gases when it is struck by the
firing pin.
In Boxer primed ammo there is only one flash hole as compared to Berdan Primed ammo that usually has two smaller flash holes.
Primer powered ammunition usually have enlarged flash holes as it is only the ignition of the primer that is used to propel the light projectile. Cases modified for this function should no longer be reloaded to fire full charge service ammunition.