Wool,
Gona depend. First up for bids is the 45 Schofield in a 45 Henry. There is no modification required to shoot Schofields. However, there is a caveat. You can't shoot bullets any shorter than a 200Gr RNFP. Any shorter and you get a double load to the carrier that jams the rifle.
The Carbon build up at the case mouth may well depend on your choice of powder. When I used that Heathen Fad Smokeless stuff, I used TightGroup. For Years. Never had "ring around the chamber."
Also modified Several Henry rifles for C45S. It takes a carefully placed setscrew in the Carrier Block and clearance channel in the side of the Breach Block. Same result as the Schofield with TightGroup. No ring around the chamber. Other powders may give you different results. Trailboss leaves ring around the chamber.
When I gave up on Smokeless, I switched to APP. Neither BP nor APP has left ring around the chamber. Go For It!!
Coffinmaker