Winchester NATO-Spec Armed forces Primers forty one are the exact same primers used in the Lake City 5.56mm ammunition. These primers are crafted to exacting specifications for shot to shot consistency. All primers are consistently and rigorously examined for consistency and sensitivity at temperatures and problems significantly further than the range of regular usage. Winchester assures carefully-managed weights of primer mixtures, consistency in dimension and top quality, precise measurements and tolerances for anvil heights and steadiness in winchester 41 primers extremes of temperatures and humidity.