Bartlein will do what they call a #0 ”Featherweight #2” in stainless, which I believe has a straight taper from the shank to the start of the barrel taper. It has to do with the barrels that use sweeping transitions from shank to the beginning of the barrel taper being too thin in the chamber area for all possible chambers.
A good smith can turn you a lean barrel based on your shank and chamber characteristics.
