A semi-automatic shotgun is a kind of gun. It fires one shotgun shell every time the trigger is pulled. Most shotguns, such as pump-action shotguns, lever action shotguns, and break barrel shotguns, use no energy from the last fired shell to load the next one. A person using a semi-automatic shotgun has to load the first shell themselves. The rest of the shells are loaded by the gun using part of the energy used to fire each shell. 