Winchester NATO-Spec Navy Primers forty one are precisely the same primers Employed in the Lake Metropolis 5.56mm ammunition. These primers are created to exacting requirements for shot to shot consistency. All primers are consistently and winchester 41 primers rigorously tested for regularity and sensitivity at temperatures and disorders considerably further than the number of normal use. Winchester ensures very carefully-controlled weights of primer mixtures, regularity in dimension and high quality, exact measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.