Winchester NATO-Spec Military Primers 41 are the same primers used in the Lake City five.56mm ammunition. These primers are constructed to exacting specs for shot to shot consistency. All primers are winchester 41 primers continuously and rigorously tested for regularity and sensitivity at temperatures and disorders considerably outside of the number of ordinary utilization. Winchester guarantees cautiously-managed weights of primer mixtures, consistency in size and high-quality, exact measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.