Common to all standard M16/M1, Garand, M14, SKS and AK47 pattern firearms, due to inertia firing pins. One of the reasons that mil-spec ammo requires specific primer construction. Slam fires can occur while loading, so it is IMPERATIVE that the firearm be pointed in a safe direction when loading a round into the chamber. Also, NEVER, drop a round into the chamber and then hit the bolt release, allowing the bolt to run forward onto the chambered round under full power, that increases the chances of a slam fire. By having the bolt strip the round out of the magazine, it slows the bolt's forward inertia and lessens the impact of the tip of the firing pin onto the primer.