Ive got an old. 20 gauge bolt action shotgun and for some reason the bolt is tough to open or close. (Almost impossible to shut it or open it with a shell in there). What would cause this? the gun calls for 2 3/4 shells and thats what I use, So i dont know what it would be. This gun is really old and im thinking it has something to do with the actual bolt itself but i dont know what. Anyone got any ideas???