Winchester NATO-Spec Armed forces Primers forty one are the identical primers Employed in the Lake Metropolis 5.56mm ammunition. These primers are built to exacting technical specs for shot to shot regularity. All primers are frequently winchester 41 primers and rigorously analyzed for consistency and sensitivity at temperatures and circumstances far past the variety of normal utilization. Winchester assures diligently-managed weights of primer mixtures, regularity in measurement and excellent, precise measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.