I had some stock work done on a 16 gauge L.C. Smith, Damascus hammer gun. That part is done. However, I'm told that the screw that holds the top lever to the rotary bolt has stripped threads and won't hold when he tries to reassemble it. He doesn't know if the screw is even original to the gun. So, does this screw come in from the top externally or from inside? Is this screw something I might be able to find or have made? Thanks, Dave