IIRC, the 627 .38super's weren't known for their accuracy. The round itself was fine, but the bore on these guns were a tad oversized, as S&W simply used .357 barrels.
As far as a custom build, I agree Hartshorne is likely a good place to start. Another would be Randy Lee at Apex Tactical. He's the
go-to gunsmith for competitive wheelgunners.
Originally Posted by Magnum Wheel Man
but what if any advantage would the 38 Super have over 38 Special or 357 magnum with the revolver machined for moon clips ???
The shorter round makes for quicker reloads. Given the issues above, coupled with the scarcity of the 627 .38 Super, most competitive shooters who use an uncompensated 627 loaded to minor power factor simply load .38 Short or Long Colt cases, or shorten .38spl cases to some custom length between the 2.
Also the OP mentioned they want a compensated gun, and the .38Super (loaded hotter than the loads mentioned above) works well in this regard.