Many new shooters are confused by the idea of a single-action semi-automatic gun, so we’ll explain. Although a semi-automatic firearm ejects the empty cartridge and reloads another round, each trigger pull still only performs one function: firing the weapon. It is the operating mechanism of the gun that recocks the hammer.nnTo compare, standard double-action does not automatically recock the hammer after a shot is fired. The trigger must be pulled again to perform the double function of cocking the hammer and firing the gun.