Winchester NATO-Spec Army Primers forty one are exactly the same primers Employed in the Lake Metropolis five.56mm ammunition. These primers are developed to exacting specifications for shot to shot regularity. All primers are constantly and rigorously analyzed for consistency and sensitivity at temperatures and ailments much outside of the range of typical utilization. Winchester assures cautiously-controlled weights of primer mixtures, regularity in measurement and excellent, specific measurements and tolerances for anvil winchester 41 primers heights and steadiness in extremes of temperatures and humidity.