Winchester NATO-Spec Navy Primers forty one are exactly the same primers used in the Lake Town 5.56mm ammunition. These primers are designed to exacting requirements for shot to shot consistency. All primers are constantly and rigorously analyzed for consistency and sensitivity at temperatures and conditions considerably over and winchester 41 primers above the variety of standard use. Winchester ensures very carefully-managed weights of primer mixtures, consistency in dimensions and top quality, specific measurements and tolerances for anvil heights and balance in extremes of temperatures and humidity.