I had to do the same thing. What I think GMB does is put the same thimble rib on all their barrels. This barrel, being so short, required more taken off. I had to cut off the same amount, turn the ramrod tension spring, and then I took some Birchwood Casey Barrel Black (felt tip marker pen) and painted the cut off part. You'd never see it because it fits against the stock. I used my dremel tool also, but I think I could have carefully done it with a hacksaw. If people still use them things..