Winchester NATO-Spec Military Primers forty one are the exact same primers Employed in the Lake Metropolis 5.56mm ammunition. These primers are created to exacting requirements for shot to shot consistency. All primers are continually and rigorously tested for regularity and sensitivity at temperatures and ailments significantly over and above the variety of typical usage. winchester 41 primers Winchester ensures meticulously-controlled weights of primer mixtures, regularity in dimension and high quality, exact measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.