These primers are #41 Small Rifle Primers used by the Military, and OEM small arms manufacturers, comparable to the CCI No. 41 primers.  These non-corrosive, all weather primers deliver fast, dependable ignition under any shooting condition. Primers are constantly and rigorously tested for consistency and sensitivity at temperatures and conditions far beyond the range of normal usage. Winchester guarantees better sensitivity for more positive firing in all guns, 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.