Bob, I've burned a ton of Pyrodex, both P in my pistols and revolvers and RS in my rifle (Lyman Trade Rifle). I've experienced no issues with it, other than you need to clean your guns the same day you shoot 'em and oil the clean metal well, afterwards. You'll find the Army will generally take between 30 and 35gr behind a .454 round ball, a bit less if you're gonna try to shoot conicals (generally 30 grains or so). There were some (IMHO unfounded) theories and rumors running around the 'net a few years back about Pyrodex causing "micro-pits" in some high end barrels, but for your garden variety Pietta it will do just fine. One thing about Pyrodex; it's non-progressive fouling, which means it won't continue to build up worse and worse fouling as you shoot. You will generally get through a complete shooting session without anything needed beside an occasional wipe down. Cleanup is easy and simple with warm, soapy water as with Black Powder.
One thing; store Pyro in the original container and keep it tightly sealed. Humidity will weaken it over time. I'd try out a few shots with the open container, then compare them to some from the fresh container. If there is a notable difference in sound, recoil, and bullet placement on paper, you might be better dumping it in the flower bed.
Hope this helps.
