Winchester NATO-Spec Military Primers 41 are the same primers Employed in the Lake City five.56mm ammunition. These primers are developed to exacting specifications for shot to shot consistency. All primers are continuously and rigorously examined for regularity and sensitivity at temperatures and situations considerably past the selection of normal usage. Winchester ensures cautiously-controlled weights of primer mixtures, consistency in dimensions and high quality, exact winchester 41 primers measurements and tolerances for anvil heights and security in extremes of temperatures and humidity.