I have a Mossberg 500 that was seriously rusted. But it was only on the outside of the barrel. It was mounted on a wall for about 5 years with an evaporative cooler blowing on it. I bought it really cheap. I am going to convert it to a pistol grip and cut down the barrel. Right now the thing is just shy of 50" long. I have already cleaned up the rust with an SOS pad. I purchased the grip and forearm this afternoon. I hope to put it together tonight. I will post some pics later. I am going to cut the barrel down to 18 1/2 inches. I am still trying to decide how I want to refinish the barrel. I was thinking of using one of those cold blueing kits. Anybody here use one with good results?