I got a Taylor 1873 lever with 24" barrel chambered in 357mag and that has to be one of the best in my opinion. I love the 357mags versatility and the 1873 is such a smooth action that i find myself cycling it just for the feeling.

Black powder has become a little hard to come by lately so I have started to look into the substitutes like Pyrodex and 777. Does anybody have any experience with those especially in cartridge loads like the 45-70?

In my limited experience i think it comes down to this
Heavier bullet = more momentum, better penetration, less drop at distance, but slower velocity and more recoil.
Lighter bullet = higher velocity, flatter trajectory, less recoil, but less penetration and more wind drift.