Winchester NATO-Spec Military services Primers 41 are the exact same primers used in the Lake Town 5.56mm ammunition. These primers are built to exacting requirements for shot to shot regularity. All primers are regularly and rigorously tested for consistency and sensitivity at temperatures and disorders much further than the variety of normal usage. Winchester ensures carefully-controlled weights of primer mixtures, consistency in dimensions and high quality, precise measurements and tolerances for anvil heights and security in extremes winchester 41 primers of temperatures and humidity.