For deer hunting, what do you really need with a .45-70?
The 1876 Winchester .45-60 factory load was 60 grains of black powder and a 300 grain soft cast round nose bullet at 1315 FPS, which hunters back then used on elk, moose, and black bear. This in a 26" barrel rifle.
The Ideal (Lyman) 330 grain soft cast round nose hollow point at around 1275 FPS was also popular. Considering the velocity and bullet and appearance it's sort of emulates a giant version of the .22LR.
In a .45-70 you could use about 28 grains of AA5744 with a soft cast 350 grain round nose flat point bullet to get around 1250 FPS for deer hunting. AA5744 is not position sensitive, so velocity is pretty constant.
Low recoil and all that you need for deer within 100 yards or so.
I don't need my 45-70's 405 gr load (moving along ~1500-1600 fps) for deer. I hunt with it for deer because I never know when the 300-400 lb+ feral hog is going to show up, needing dispatching.
Deer aren't armor-clad nor bullet proof. However, in many places, they range alongside some serious predators and scavengers you don't want low-percentage shots with.