An attachment firing apparatus, in particular a grenade launcher, for mounting on the barrel of a firearm, having an anchoring part that can be fixedly mounted on the firearm and having a support part that can be detachably connected to the anchoring part via a coupling, a launch tube in the support part being openable and closable relative to a breech, wherein the coupling is locked in the closed position of the launch tube and breech and can be opened in the open position of the launch tube and breech.