Abstract: A double action safety lock mechanism is disclosed for use in a two barrel firearm. Fixed firing pins on a frame member are struck by a pivotally mounted hammer carried on a pivotally movable trigger plate member and engaging a sear member attached to the frame member. Extra security and safety is provided by a key controlled locking system capable of rendering the entire firearm lock immobile. Means are also provided for selectively firing only one of the two barrels of the arm at a time.