Seen lots of data about the web on using pyrodex in the more common cartridges.
Pyro and BP can be messy especially when mixed with lube, so repetitve shots gums you up more and more.
I have had a few contacts with Hodgdons about 777 in cartridges. They have not published "official" data yet on all cartridges though there are some experimenters filling in the gaps. The beauty of 777 is that you can lube with Alox so gumming is nowhere near as bad and repetitive shooting without cleaning is possible.

I load 38spl and .357mag with 777, the data says fill to the bottom of the bullet so as not to leave an airgap. Its a much lighter bang so breech pressures should be within safty margins of a modern nitro proofed barrel. But dont take that as gospel, do some proper research before you try it.