BR,
Ammo selection will have a BIG effect on the .45-70. If you load it like a "poor man's" .458 Win Mag you're going to lose LOTS of meat! Loaded to "standard" velocities (like the old 405-gr factory loading) with hard-cast bullets that have large, flat noses or appropriate soft/hollow point bullets you can, as Elmer Keith liked to say, eat right up to the hole. Enjoy!