Dont try it with a Old Model barrel unless you want to have a custom ejector housing made. The mounting screw is located in the wrong position. I put an Old Model 4 5/8" barrel on one and ran into the problem. I made one up in cad and could of had my friend wire burn one out for me and then finished it up but then decided to just go back to the original barrel. the location of the screw on the housing just looked odd. I have bought barrels from Hamilton Bowen from Bowen Classic Arms for a very reasonable price in the past. He pulls barrels from guns that get caliber changes all the time and has them laying around.