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 specifications for shot to shot consistency. All primers are regularly and rigorously analyzed for regularity and winchester 41 primers sensitivity at temperatures and conditions much over and above the number of regular usage. Winchester guarantees very carefully-controlled weights of primer mixtures, consistency in measurement and high-quality, specific measurements and tolerances for anvil heights and steadiness in extremes of temperatures and humidity.