Winchester NATO-Spec Military services Primers forty one are the exact same primers used in the Lake City 5.56mm ammunition. These primers are designed to exacting specifications for shot to shot consistency. All primers are winchester 41 primers continually and rigorously examined for regularity and sensitivity at temperatures and disorders far past the variety of usual use. Winchester assures carefully-managed weights of primer mixtures, regularity in sizing and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.