I don't know much about this 15-3. It has a ball lock/detent in the crane and weighs 56 oz. The rib seems to be just a normal scope mount that was designed for S&W's because it has a screw hole that matches up to the rear sight screw. It is attached to the barrel with 3 screws. Its SAO and the trigger breaks at 1.5 lbs. It is very accurate. The grip really helps with the heavy front end. It's not quite at the level of sophistication of the guns pictured earlier in the thread. I added the trigger stop
. Pencil eraser, Duco cement, adjusted with emery board.