Winchester NATO-Spec Military services Primers forty one are a similar primers used in the Lake Metropolis 5.56mm ammunition. These primers are crafted to exacting specifications for shot to shot consistency. All primers are regularly and rigorously analyzed for regularity and sensitivity winchester 41 primers at temperatures and circumstances much outside of the number of regular usage. Winchester guarantees very carefully-controlled weights of primer mixtures, consistency in dimension and top quality, exact measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.