Winchester NATO-Spec Military services Primers forty one are a similar primers used in the Lake Metropolis five.56mm ammunition. These primers are crafted to exacting specs for shot to shot consistency. All primers are regularly and rigorously analyzed for regularity and sensitivity at temperatures and conditions much winchester 41 primers over and above the number of normal usage. Winchester guarantees cautiously-controlled weights of primer mixtures, consistency in size and high quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.