Winchester NATO-Spec Armed service Primers forty one are the exact same primers used 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 examined for regularity and sensitivity at temperatures and conditions far over and above the number of normal usage. Winchester guarantees meticulously-managed weights of primer mixtures, regularity in dimensions and high-quality, specific measurements and tolerances for anvil heights and steadiness in extremes of winchester 41 primers temperatures and humidity.