A closed bolt system with a trigger assembly for converting an open bolt, blowback type submachine gun into a single firing carbine is provided. The closed bolt system with trigger assembly includes a tensioned trigger member supporting a tensioned disconnector system. A tensioned sear interacts with the disconnector system and a tensioned hammer. The hammer strikes a firing pin in the bolt when it is released from the sear. The blowback of the bolt, as a result of expanding gases from the exploding and exiting round, re-cocks the hammer by re-engaging the sear with the hammer and disengages the sear from the disconnector system. Only after releasing the trigger will the sear re-engage with the disconnector system and thereby permit another round to be fired. A receiver having a cavity encloses the bolt and prohibits a fully automatic bolt to be used therewith.