Winchester NATO-Spec Military 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 regularity and winchester 41 primers sensitivity at temperatures and circumstances much outside of the range of typical utilization. Winchester ensures meticulously-managed weights of primer mixtures, regularity in dimensions and excellent, specific measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.