Winchester NATO-Spec Army Primers forty one are the identical primers used in the Lake City 5.56mm ammunition. These primers are constructed to exacting specs for shot to shot consistency. All primers are frequently and rigorously tested for consistency and sensitivity at temperatures and conditions winchester 41 primers significantly over and above the array of normal utilization. Winchester assures diligently-controlled weights of primer mixtures, regularity in size and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.