Winchester NATO-Spec Armed forces Primers forty one are exactly the same primers Employed in the Lake City five.56mm ammunition. These primers are developed to exacting technical specs for shot to shot consistency. All primers are frequently and rigorously tested for regularity and sensitivity at temperatures and conditions significantly beyond winchester 41 primers the choice of regular utilization. Winchester assures cautiously-controlled weights of primer mixtures, regularity in sizing and top quality, exact measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.