I have a bit of history with the 45/70. Frank Siefer, an old friend of mine (sadly, gone to the Range in the Sky), put me on to a late model Marlin with conventional rifling. I found it very easy to work up a load after I made some necessary changes in the Marlin. It was issued with a curved steel butt plate. When I got it, it was in the hot summer time. The only loads I had were full case black powder/Reloader 7 Duplex loads with the a 500 grain bullet. I was wearing a "T" shirt and when I was finished trying my rifle out for the first time, my right shoulder was bloody! Yeah, RIGHT!
I immediately drove home, did a bit of online shopping, drove to the nearest purveyor of quality recoil pads and picked up a good one. I got on the phone, called a stockmaker friend of mine, and IMMEDIATELY took my newly acquired 45/70 and drove to his home/shop. I knew my preferred measurements, he cut off the stock, and installed the new pad.
After a few days of healing, I went to the range with the exact same loads and fired my new gun. It was a PLEASURE to shoot.
A couple of my buddies suggested I had done a BAD thing. "Think about re-sale", etc. Me, I knew I had done the RIGHT thing.
That became a very nice and practical rifle and should work for the largest of big game. After all, the Bison were nearly wiped out in the west with the 45/70 and equivalent rifles, etc.
At the time, Ohio did not permit modern rifles in the taking of deer. We now had LOTS of deer, many farmers would be HAPPY to have a hunter harvest any number of them, but no modern rifles were allowed. Now, that in itself, meant little to me as I was quite happy to harvest my deer with my .44 magnum handguns. Frankly, in the wooded country I hunted in here in SW Ohio, I didn't need anything else.
However, I really wanted to try the 45/70 on deer. I had obtained a Lyman Gould 457122 hollow point mould (about 330 grs in my alloy) and had a black powder equivalent load with RL-7. RL-7 was a near perfect powder for the purpose. It is about the speed of 4198 but it measures much better. That's what I used for Duplex loads in my single shot rifles in .40/65, .45/70, and .45/90, so I had plenty on hand. I had no problem getting under 2", on demand" at 100 yards with a low powered scope on the rifle.
About the time I lost the vision in my right (shooting) eye, Ohio opened up deer hunting to straight wall rifle cases. Remember that old saying, "Timing is everything", well it certainly applied to my 45/70's. Yeah, I also had a Ruger #3 in .45/70, complete with a new recoil pad and scope all set for the new deer season.
No complaints, tho', I did learn a good bit. I eventually sold nearly all of my long guns, including all of my 45/70's. Pardon me, please, while I wipe a tear away (must be the spring allergies, huh?)...