Winchester NATO-Spec Military Primers forty one are the identical primers Employed in the Lake Metropolis 5.56mm ammunition. These primers are developed to exacting technical specs for shot to shot consistency. All primers are continuously and rigorously analyzed for regularity and winchester 41 primers sensitivity at temperatures and situations significantly outside of the array of ordinary utilization. Winchester ensures very carefully-controlled weights of primer mixtures, consistency in size and excellent, exact measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.