My experience with reloading 45/70 is for the Trapdoor Springfield, which has three lands/three grooves, all shallow, equal width (basically, still Minie bullet technology barrels). 70 grains of 2F fills almost to the brim, so the powder has to be compressed. With SPG lube, to the best of my memory, this compressed load shoots pretty clean and is very close to the original load if you use the correct bullet. Takes a Federal large magnum rifle primer to set it off correctly. There was a book written by a now-departed fellow named Wolf on loading and shooting the trapdoor, using a reproduction of the federal cartridge of the time. It is a gold mine if you want to repro the old way, but your barrel's rifling will tell you if you can or not - you'll be shooting medium hard lead, about 1200fps. Shallow rifling would be the trick, and you either need to use the 500 grain rifle bullet or the 405 grain hollow base to grab the rifling right (the inertia of the 500 grain keeps you from having to have a hollow base - the base will expand by itself into the grooves when fired).
The joys of 45/70. Indescribeable...