I believe that Pyrodex can be used at the same volume as BP BUT I've never used it so don't take it as gospel. I normally use 25gn fffg in my .45 and I've been asked "what load are you using to reach earthquake mode".

Mr. Foley has more experience than I do with BP pistols so I would listen to him regarding loads. Although I've been using BP in shotgun loads since the mid 80s, I've only been using pistols for the last few years.