I think that pre-Civil War firearm innovations were just amazing before the advent of the metallic cartridge era just afterward. Colt, Remington, Manhattan, (as well as Gatling) and other players made a huge difference compared to the percussion single-shot pistols that preceded them. Yes, I know that the Spencer and the Henry rifles were there, but not in great quantity, and therefore, not a large player.
The Treeby gun is a new one on me. A shooter would definitely need a second rifle with a loader behind him. Since only 2 were made, that was probably never put into practice, and not very practical. Innovative, yes. In a tactical situation, very clumsy concerning the machinations required to operate it.
Three .44 Dragoons, 1860 .44 Colts, or even 1851 Navy .36 pistols would have served better.
Quite an innovation though, I must say.
Jim