BUFF, two things to remember about Pyrodex. First, it is almost as corrosive as BP, since is has sulfur in the powder and also leaves moisture attracting residue in the bore. Second, is it hotter than BP and when shooting antique guns, slightly reducing the load would be prudent. There are non-corrosive powders out there like Triple 7, Pinnacle, and Clean Shot. These powders are all measured by volume and not weight. I have chronographed all of these loads and find that BP is the slowest, Pyrodex is faster, followed by Clean Shot, and 777 is the fastest.
There are still lots of misconceptions about the burn rate for smokeless powders out there, but you can put together loads with smokeless powders that are lower in pressures than BP. Many members of this forum recommend and shoot smokeless 32rf, 32 S&W, 38 S&W, etc. in old S&Ws with good success. They are mild loads and are actually lower in felt recoil and velocities than original BP rounds.
It is perfectly understandable to go with the original BP loads in these old revolvers, but I am just saying that there are loads out there that will duplicate BP without the mess and cleanup. I have posted these charts before and they are from a Double Gun article by Sherman Bell that gives examples of pressures over the length of a shotgun barrel. I just wish I could find some testing research on handguns, but my experience is that you can duplicate ballistics and pressure curves with smokeless powders.