This won't be terribly helpful, but in 1980 I was told by a fourth-rate gunsmith that my Model 64's chambers could be bored out and shoot .357s "no problem." Back then you could send the NRA a self-addressed stamped envelope and ask technical questions, so I asked about it. The guy who wrote back said he didn't know about the stainless guns, but he said he knew that both the steel and the heat treatment in the Model 10 and 19 cylinders were different. I've no way of knowing if he knew what he was talking about.

It would seem to me that possibly Mr. Jinks would know, or could find out.