Ted, have you slugged your barrel? Before you buy a bushing, I would slug the thing to find out where you are starting from. The Merkel I work with has a .474 but Krieghoff might be different. .002 over is not too much. As much hell as a 470 Nitro raises when you shoot it, the pressures are not all that high, just a LOT of boolit and powder heading out the spout!