Winchester NATO-Spec Armed service Primers 41 are the identical primers used in the Lake Metropolis five.56mm ammunition. These primers are created to exacting specifications for shot to shot regularity. All primers are continuously and rigorously analyzed for regularity and sensitivity at temperatures and problems far outside of the winchester 41 primers selection of ordinary usage. Winchester ensures diligently-controlled weights of primer mixtures, consistency in measurement and quality, precise measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.