Winchester NATO-Spec Armed forces Primers forty one are the exact same primers used in the Lake Metropolis five.56mm ammunition. These primers are constructed to exacting requirements for shot to shot regularity. All primers are continuously and rigorously examined for regularity and sensitivity at temperatures and disorders far over and winchester 41 primers above the number of typical utilization. Winchester ensures diligently-managed weights of primer mixtures, regularity in size and top quality, exact measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.