Winchester NATO-Spec Army Primers 41 are exactly the same primers Utilized 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 usual use. Winchester assures diligently-managed weights of primer mixtures, regularity in sizing and high quality, precise measurements and tolerances for anvil heights and winchester 41 primers stability in extremes of temperatures and humidity.