Howdy
I only shoot Black Powder through all my Cowboy Action guns. Revolvers, rifles and shotguns. 45 Colt, 45 Schofield, 44-40, 44 Russian, 45-70 and 12 Gauge. Colts, Rugers, Ubertis, Winchesters, Marlins, Stevens.
However I wouldn't dream of shooting Black Powder through most of my modern guns. Black Powder requires more dedication than Smokeless. You really have to clean them every time you shoot them. You actually don't have to run home and clean them the same day, but you do have to clean them every time. In addition, it is more expensive to shoot Black Powder. Usta be that BP was significantly cheaper than Smokeless, but since the charge is so much bigger, you burned up a lot more powder and it wound up costing more. But these days, BP costs almost as much as Smokeless. I just paid $16/pound for the last few pounds of Schuetzen I bought. When you consider I will only put about 7.5 grains of Unique in 45 Colt or 44-40, but I but about 35 grains of FFg in the same two cartridges, the powder cost quickly skyrockets.
As if that were not bad enough, you can't use conventional bullets lubed with conventional hard bullet lube with Black Powder (real Black Powder, not the substitutes). You either have to make some allowance to get some soft lube into the cartridge, or lube your bullets with a BP compatible bullet lube. I cast my own bullets for all my BP cartridges, and size them and lube them with SPG.
All in all, it makes for a lot more work to be shooting Black Powder. It's great fun, but it requires more dedication than shooting Smokeless. I am very happy to shoot Smokeless in my modern guns and just give them a quick wipe down and put them away in the safe at the end of the day.
P.S. Did I mention that all my BP brass gets soaked in a jug of water with a few drops of dish soap. If you don't soak the brass it WILL corrode with 24 hours. With Smokeless I just wait until I have enough of a particular caliber, then dump them in the tumbler. No need to rush right home and do it.