I've been shooting 45-70 since 1983. It is very affordable to reload! But it is a large cartridge! so the marketers seem to think it should be sold for big money! I currently have 4 rifles (1974 Shilo Sharps, M-1873 Cav Carbine from 1875, a Browning 1886 from 1986, and a first year JM Marlin Guide Gun.)
Loadings: Loading manuals list 3 strength levels for 45-70. All common factory ammo is loaded to the lowest level (1873 Trapdoor)
I load a light plinking load, a Black Powder load, and a pretty massive anti bear load (That is safe in the 1886 and Marlin category)
Loading realities: E=M C squared! Both the Energy and the felt recoil increase with any additional velocity or bullet weight! If you stick to 300 grain bullets around 1300 fps (black powder velocity), it will be a pleasant and mild gun. My bear load is 400 grains at 2200 fps and kills on both ends. Loading accurate 45-70 ammo with any bullet weight at the 1300 to 1700 fps level, it is hard to come up with an inaccurate load! Consistency is your friend! Common factory ammo doesn't seem to follow that rule!
Ivan