Winchester NATO-Spec Navy Primers forty one are a similar 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 consistency and sensitivity at temperatures and situations significantly further than the selection of winchester 41 primers standard utilization. Winchester guarantees very carefully-controlled weights of primer mixtures, consistency in dimension and good quality, exact measurements and tolerances for anvil heights and security in extremes of temperatures and humidity.