Here's a third combo that produces a fouling ring the chambers: 45 S&W (Schofield) in a .45 Colt cylinder.
My OM BH won't accept the Schofield cases due to the rebated chambers, but my Uberti Cattleman will. To date I've fired less than a full box of Schofields in it and I can still see ring even after thoroughly cleaning it. The Uberti seems to have tighter chambers than the Ruger so it "might" become a problem if I fired enough of them then switched to the longer .45 Colt round.
As for shooting 38s in a .357 I really hate to do it. Have done, do it, but only because I've got a ton of 38 ammo and no dedicated 38 revolver to shoot it from.
The .45 Schofield in the .45 Colt was an experiment to see what sort of accuracy I'd get with the shorter round.
Worked good.
Joe