The difficulties and drawbacks of previous-type systems are overcome by the present invention which includes a locking device for a firing spring housing in a firearm. A main housing is provided including an internal cylindrical portion for receiving a firing spring. A lock rod is received in the main housing, for selectively engaging the firing spring. The lock rod is movable between an engagement position and a disengagement position with the firing spring. A combination disk is provided for engaging the lock rod, to selectively fix the lock rod in one of the engagement position and the disengagement position.