Winchester NATO-Spec Military Primers are the same primers used in the Lake City 5.56mm ammunition. These primers are built to exacting specifications for shot to shot consistency. All primers are constantly and rigorously tested for consistency and sensitivity at temperatures and conditions far beyond the range of normal usage. Winchester guarantees carefully-controlled weights of primer mixtures, consistency in size and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.