I have a line on a Sig 229 pistol I might like to buy. The only problem is it's in .40 S&W and I really want a .357 Sig. I know the barrels on these can be swapped out, but is it truely a drop in deal with no smithing involved? Are the magazines the same for the .40 and .357 guns or do they need to be swapped out as well? I'm a 1911 guy and the Sig stuff is new to me. Thanks!