I have had several rounds explode when they were dropped into the chamber of the appropriate weapon and the hammer fell striking the firing pin which, in turn, struck the primer and caused a terribly loud blast out of the muzzle and caused the bullet to travel at high velocity until it passed through a paper target and impacted the berm. Seriously, accidental detonation of ammunition from being dropped is EXTREMELY rare. Even in a fire the worst thing that happens is the primer pops out and the powder flares off feeding the fire. There is no danger unless the ammunition is contained by the weapon's chamber and the round "cooks off" sending the bullet out of the muzzle at the normally expected velocity.