They are about 180 bucks, and any smith with 12ga 3.5" reamer can do it, or if you have reamer and some experience using reamers you can do it. Don't have to go to the bother of dealing with factory, which isn't in US anyway. The reason I know the gun can be chambered longer is that Rossi barrel is built like NEF slug barrel and also Rossi makes a turkey/goose gun for magnum loads in 3.5" that has a thinner barrel than this slug gun.Ed