While the .32-40 is certainly not the only choice for 200 yard match rifle shooting with black powder, the following overview explains its historical popularity.
The .32-40 was introduced about 1884 and right from the git-go started to catch on with Schuetzen shooters. From about 1890-on, Schuetzen started becoming a .32 caliber game (especially among the top tier shooters). Until the mid-1890s, offhand target shooting was all with black powder. Viable smokeless and semi-smokeless powders hit the scene around 1895-97. This is when duplex loading began to dominate the Schuetzen game (again, especially among top tier shooters).
So . . . what’s the relevance of my abbreviated history lesson? The .32-40 was accurate enough with black powder to dominate the Schuetzen game over the larger calibers during its heyday and the introduction of duplex loading securely cemented that dominance until Schuetzen faded into history and improved smokeless powders came to displace black powder loading.
To learn more, this is all thoroughly detailed in my book “The Golden Age of the American Schuetzenfest”.

GWarden, I figured you'd chime it.   What sort of bullets gave you the best results with BP?  i.e. have you compared spitzers vs Pope style?

I don't think I've ever used anything but Pope style bullets with BP.  Either Hoch 200gr one, the Saeco 200gr one, and a Brooks hybrid of the two.

Chris.