Firearms have an alignment element configured to connect to the barrel with the threaded muzzle portion exposed forward of the alignment element, the alignment element having a lock element movable between a release position and an engaged position, a muzzle device having internal threads configured to mate with the threaded portion of the barrel, the muzzle device defining a lock channel adapted to receive the lock element in the engaged position, the lock channel including wall portions configured to contact the lock element in the engaged position to prevent rotation of the muzzle device, and the lock element in the release position being clear of the lock channel to enable the muzzle device to rotate for removal from the threaded muzzle portion. The alignment element may define a first bore portion configured to closely receive a selected barrel portion immediately aft of the shoulder surface.