Winchester NATO-Spec Armed service Primers forty one are the exact same primers used in the Lake City five.56mm ammunition. These primers are created to exacting specs for shot to shot consistency. All primers are frequently and rigorously tested for consistency and sensitivity at temperatures and situations much past the choice of typical usage. Winchester winchester 41 primers ensures meticulously-managed weights of primer mixtures, regularity in dimensions and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.