The Winchester Large Pistol Match Primers are identical to the primers used in the Winchester USA Ready ammo. This primer is manufactured to stringent standards to ensure uniformity from shot to shot. Constant and extensive testing is performed on every primer to ensure that it remains consistent and sensitive even when subjected to conditions that are outside its typical operating range. Winchester promises increased sensitivity for positive firing in all firearms, uniformity in size and quality, accuracy in measurements and tolerances for anvil heights, and durability in harsh climates.