Winchester NATO-Spec Armed forces Primers forty one are the identical primers Employed in the Lake City 5.56mm ammunition. These primers are designed to exacting specifications for shot to shot consistency. All primers are consistently and rigorously analyzed for regularity and sensitivity at temperatures and conditions much over and above the number of regular usage. Winchester guarantees meticulously-controlled weights of primer mixtures, consistency in measurement and excellent, winchester 41 primers specific measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.