I have been saying this for years, but I will say it again.
Black Powder is no where near as corrosive as most shooters think.
Back when corrosive primers were standard, the combination of corrosive primers and BP fouling was very corrosive.
We don't use corrosive primers any more.
If left uncleaned for 24 hours, a modern revolver fired with Black Powder will not disintegrate into a pile of rust. I don't shoot much CAS these days, but when I do, it is always with cartridges loaded with Black Powder. 45 Colt in my Colts, 44-40 in my Henry rifle, and 12 gauge in my shotgun. I NEVER clean them the same day I shoot them. Cleaning four guns after shooting all day and driving home a couple of hours is more than I want to do. My standard was to try to clean them within a week of shooting them. I will not state here publicly how long I have actually gone without cleaning my guns, but I can tell you it was much more than a week. When I got around to cleaning them, they were not reduced to piles of rust.
I will say it again, non-corrosive primers are the secret.
Go into a museum sometime and look at an old Flintlock rifle. There will be very little corrosion around the flash hole because corrosive primers were not being used. Then take a look at an old Cap & Ball rifle. There will be much more corrosion around the nipple, because of the corrosive primers used back then.
Anyway, here is a photo of the Stainless Ruger Old Army I picked up a few years ago. No rust with modern caps.