Winchester NATO-Spec Military services Primers 41 are the same primers Utilized in the Lake Metropolis five.56mm ammunition. These primers are constructed to exacting specs for shot to shot regularity. All primers are continuously and rigorously analyzed for consistency and sensitivity at temperatures and situations much over and above the number of regular use. Winchester assures very carefully-managed weights of primer mixtures, regularity winchester 41 primers in size and high quality, precise measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.