if you read the history of target shooting, you'll find that in the late 1800's they were still using Muzzle loaders even as the black powder cartridge guns like Remington rolling block or sharps came into being. Such as the 800 to 1000 yd matches at Creedmoor long island in 1876.
Such guns used a "false muzzle" to guide the bullet into the rifling when loading, and absolutely HUGE barrels, like 2" across the flats. I've seen things like that
there are still folks experimenting with such things, go visit a club with an active black powder group...
shoot good
Poole
http://arizona.rifleshooting.com/