I have an old Remington Mod. 510 single shot that has been my yard gun for years. It has recently developed an irritating issue. When ejecting a shell the bolt will stick to the rear and you have to remove the bolt, re-insert it and then it will close. I don't see any marks on the bolt indicating binding. If your careful and slowly slide the bolt back it doesn't happen. Anyone have a clue as to what is going on? It's getting to be a pain!