Winchester NATO-Spec Military services Primers forty one are a similar primers used in the Lake Metropolis 5.56mm ammunition. These primers are crafted to exacting specifications for shot to shot consistency. All primers are regularly and rigorously analyzed for winchester 41 primers regularity and sensitivity at temperatures and circumstances much outside of the range of typical utilization. Winchester ensures meticulously-managed weights of primer mixtures, consistency in measurement and good quality, exact measurements and tolerances for anvil heights and security in extremes of temperatures and humidity.