Winchester NATO-Spec Military services Primers forty one are the identical primers Employed in the Lake City 5.56mm ammunition. These primers are developed to exacting specifications for shot to shot consistency. All primers are frequently and rigorously examined for regularity and sensitivity at temperatures and conditions much further than the choice of standard usage. Winchester guarantees very carefully-managed winchester 41 primers weights of primer mixtures, consistency in measurement and top quality, exact measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.