Winchester NATO-Spec Armed forces Primers 41 are the identical primers Employed in the Lake Town five.56mm ammunition. These primers are developed to exacting requirements for shot to shot regularity. All primers are constantly and rigorously tested for consistency and sensitivity at temperatures and problems considerably beyond the array of winchester 41 primers standard utilization. Winchester assures diligently-managed weights of primer mixtures, regularity in sizing and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.