Re: S&W 46 bbl swap. The 41 bbl will fit on the 46 frame. The 46 bbl will not fit the 41 frame unless slide is also swapped - due to lack of undercut on the 46 bbl. The bbl/slide combo can be switched either way. As noted above, the early square cut 46 slide sometimes cracked and a few early 46s can be found with a 41 slide/bbl due to this problem. In buying extra 46 bbls, need to check to see if the bbl is set for a square cut slide and you have a radius cut slide. Using a file can correct to get the correct fit.