Winchester NATO-Spec Military Primers 41 are the same primers Utilized in the Lake Metropolis five.56mm ammunition. These primers are crafted to exacting specifications for shot to shot consistency. All primers are consistently and rigorously analyzed for regularity and sensitivity at temperatures and conditions far past winchester 41 primers the choice of normal use. Winchester assures cautiously-controlled weights of primer mixtures, regularity in size and high quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.