The Lake City 5.56mm ammo uses the same primers as the Winchester NATO-Spec Military Primers. This primer is manufactured to stringent standards to ensure uniformity from shot to shot. Constant and extensive testing is performed on every primer to ensure that it remains consistent and sensitive even when subjected to conditions that are outside its typical operating range.

Winchester ensures tightly regulated primer mixture weights, uniformity in size and quality, accurate measurements and tolerances for anvil heights, and durability in harsh climates.