Semi-automatic shotgun
From Gunsopedia
A Semi-automatic shotgun is a form of shotgun that is able to fire a cartridge after every trigger squeeze, without any manual chambering of another round being required as is typical in most shotgun designs. The weapon uses the force of the gas (created by the accelerated burning of the propellant) to not just propel the wadding which pushes the shot down the barrel, but also to cycle the action, ejecting the empty shell and loading another round. This process is similar to all semi-automatic weapons, including pistols and rifles.
Many semi-automatic shotguns also provide an optional manual means of operation such as by pump-action or via a charging handle.
