CCI No. 34 primer is more sensitive, easier to seat, and more compatible with progressive and automated loading equipment than even before. CCI primers have always incorporated modern non-corrosive and non-mercuric initiator mixes. Military-style semi-auto rifles seldom have firing pin retraction springs. If care is not used in assembling ammunition, a “slam-fire” can occur before the bolt locks. The military arsenals accomplish this using different techniques and components—including different primer sensitivity specifications—from their commercial counterparts. CCI makes rifle primers for commercial sale that matches military sensitivity specs that reduce the chance of a slam-fire when other factors go out of control*. If you’re reloading for a military semi-auto, look to CCI Military primers.