Winchester NATO-Spec Military services Primers 41 are exactly the same primers Utilized in the Lake Metropolis 5.56mm ammunition. These primers are designed to exacting specifications for shot to shot regularity. All primers are constantly and rigorously analyzed for regularity and sensitivity at temperatures and disorders considerably beyond the selection of typical usage. Winchester assures thoroughly-controlled weights of primer mixtures, regularity in dimensions and high-quality, exact measurements and tolerances for anvil heights and stability in extremes of temperatures winchester 41 primers and humidity.