I am absolutely a black powder snob, and my favorite snob-powder is Swiss. That stuff burns CLEAN. Due to the price, I use it mostly (ffg) in my Jeager and black powder revolvers. I use goex fffg in my cap-gun rifles, and Goex fg in my Brown Bessie. I'm running low, so almost time to break the bank and get some more pounds of ffg and fffg Swiss. Goex I can find locally.
The only, and I mean ONLY problems I have ever had with black powder guns, was when trying fake powders. I hate them, and they suck.
They are modern smokeless powders, with junk thrown into the mix to make them smoke.