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 continually and rigorously examined for regularity and sensitivity at temperatures and conditions far over and above the choice of normal usage. Winchester guarantees cautiously-controlled weights of primer mixtures, consistency in dimension and top quality, exact measurements and tolerances for anvil heights winchester 41 primers and balance in extremes of temperatures and humidity.