[Larryjk]

Pet Loads by Ken Waters has two articles on the 45-70s; one on the rifle types and one on the different loads in three different power (pressure) levels. You really ought to read both. The loading data is mainly for smokeless powder, but you could have a hoot shooting black through that basic single shot. Black powder recoil is entirely different and velocity is around 1400 fps.
Pressures and velocity are much higher with smokeless powder.