Winchester NATO-Spec Army Primers forty one are precisely the same primers used in the Lake Metropolis five.56mm ammunition. These primers are built to exacting specs for shot to shot regularity. All primers are frequently and rigorously tested for regularity and sensitivity at temperatures and circumstances significantly outside of the range of typical utilization. Winchester ensures thoroughly-managed weights of primer mixtures, winchester 41 primers regularity in sizing and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.