Winchester NATO-Spec Armed service Primers 41 are a similar primers Utilized in the Lake Metropolis five.56mm ammunition. These primers are designed to exacting specs for shot to shot regularity. All primers are constantly and rigorously tested for regularity and sensitivity at temperatures and situations considerably past the number of regular winchester 41 primers use. Winchester assures cautiously-managed weights of primer mixtures, regularity in dimension and good quality, exact measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.