Automatics commonly work on recoil, sometimes on gas pressure. Without a bullet, recoil is less (see Newton's laws) and so is gas pressure (there's no temporary

Automatics commonly work on recoil, sometimes on gas pressure. Without a bullet, recoil is less (see Newton's laws) and so is gas pressure (there's no temporary plug in the barrel). Most semi-auto pistols will not operate with blanks unless modified in a way that would make them incompatible with regular ammo.