Winchester NATO-Spec Armed service Primers forty one are the same primers Utilized in the Lake City five.56mm ammunition. These primers are developed to exacting technical specs for shot to shot regularity. All primers are continually and rigorously examined for consistency and sensitivity at temperatures and winchester 41 primers problems significantly outside of the number of normal use. Winchester ensures meticulously-managed weights of primer mixtures, regularity in size and high quality, specific measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.