I think you can run 40 in a 10mm. It may or may not feed.
You can't run 10mm in a 40 cal for the same reason you can't run 40 cal in a 9mm. Personally, I won't substitute any round for any reason except - I occasionally run 38 special through my .357 or
44 special through my 44 magnum. That said, I'm interested in some larger loads for my .44 Mag. Buffalo Bore hard-cast.
I'm told that only three revolvers made to handle that kind of internal pressure caused by the big rounds. Ruger is one of the three. I don't know the other two. And I was told that it would destroy a colt revolver. Supposedly, not even my Henry rifle is rated for that. What about it ? Any experience with heavy rounds?