I purchased a new model 41 in 1984 with the 5 1/2 inch bull. Several years later I purchased a new 7" barrel from smith with no fitting required. The factory told me there would be not fitting required. It was just as tight as my original and removes and installs with the same fit as the original bull. But, being somewhat factory hand finished due to tight tolerances, another acquired 7" may need 'minor' fitting although I don't think it would be an issue for you.