Winchester NATO-Spec Navy 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 sensitivity at temperatures and conditions much outside of the number of regular usage. Winchester guarantees very carefully-controlled weights of primer mixtures, consistency in measurement and good quality, exact measurements and tolerances for anvil heights and security in extremes of winchester 41 primers temperatures and humidity.