A friend of mine (seriously its not me) has a 870 Express Mag. and we can't get it to take rounds in the tube. Every time it stops at the brass end both 2 3/4 and 3" rounds. I took the gun apart for him and removed the mag tube spring, but nothing looks out of place except its dirty as hell. I yelled at him for the way he let it go. We are hunting and I don't have any Rem oil. All I brought is a cleaning rag. Does this just need to be cleaned very well or have a gunsmith look at it?