Duh! Keep the chamber clean and the rifle will function. If you polish the chamber there's little left for the brass to cling to when the shot is fired and the case expands. That produces more thrust on the bolt and eventually will cause bigger problems. Chroming the chamber will reduce the chamber dimension. That's not a good thing either and may lead to problems chambering cartridges. You've hit a problem head on that our troops ran into in the sandbox. Keep the chamber clean and the rifle will function.
Just for curiosity's sake, does he carry a round in the chamber or hunt with an empty chamber. If the action is closed with a round in the chamber dirt can't get in. If the chamber is empty then you're inviting all kinds of crusty stuff to make their home there.
