Winchester NATO-Spec Military services Primers 41 are the same primers Utilized in the Lake Metropolis five.56mm ammunition. These primers are built to exacting specs for shot to shot consistency. All primers are frequently and rigorously analyzed for consistency and sensitivity at temperatures and situations significantly outside of the range of typical utilization. Winchester ensures meticulously-managed weights of primer mixtures, regularity in sizing and quality, precise measurements and tolerances for anvil heights and steadiness winchester 41 primers in extremes of temperatures and humidity.