Winchester NATO-Spec Military services Primers forty one are the identical primers Employed in the Lake Town five.56mm ammunition. These primers are developed to exacting requirements for shot to shot regularity. All primers are frequently and rigorously tested for regularity and sensitivity at temperatures and circumstances much over and above the number of normal usage. Winchester guarantees cautiously-controlled weights of primer mixtures, consistency in size and high quality, precise measurements and tolerances for anvil heights winchester 41 primers and stability in extremes of temperatures and humidity.