Winchester NATO-Spec Military Primers 41 are precisely the same primers Employed in the Lake City 5.56mm ammunition. These primers are designed to exacting technical specs for shot to shot consistency. All primers are continually and rigorously examined for regularity and sensitivity at temperatures and disorders far past the choice of ordinary use. Winchester assures carefully-controlled weights of primer mixtures, regularity in size and high quality, precise measurements and tolerances for anvil heights and stability in extremes of winchester 41 primers temperatures and humidity.