I had a Marlin 1895, fitted it with an old Weaver K2.5x Post. Great combination for me, anyway.
400gr cast at "traditional" .45-70 speed (1300sfps) were fun, and not that bad. Did load up some 385gr RN copper plated that I found, to about 1800fps.
Very effective, but the fun part went away fast. One friend of mine proved to be a stock crawler, and just as I was about to say something, fired, winning himself a "Weatherby Eyebrow".
If you want a real education in .45-70 recoil, push the Hornady 350gr RN up to 2200fps from an under 6lb Ruger No.3!
If you are going to shoot deer, and you are going to push a 400gr bullet fast (1800fps), I do
not recommend the Speer 405gr. A hard cast slug will actually be better. The Speer 405 is made to expand (some anyway) at standard blackpowder speeds, and driving it up to 1800 make it come apart too easily to be good. Speer agrees with this, and will tell you, if you ask.
Drive that same bullet to 2100fps in a .458 and it acts like a .22 varmint bullet. Just much, much bigger.
Kicks a mite, too...