I have a Ruger Single Six .22/.22 mag that has stopped working. I thought this thing was bomb proof. Apparently like all machines it can/does wear and fail. Unfortunately it happened while someone else was using it so I'm not entirely sure how it was handled/mishandled before the fault occurred. The gun is well used but has always proven reliable before. Te hammer will not cock back and in fact will barely move at all before it meets resistance. When the loading gate is open the cylinder turns freely. A small bit of metal pin approximately 2mm in dia. and 7-8 mm long was loose in the grip frame cavity it appears to be sheared off at one end. Sound familiar to anyone? Any advice?