45-70 is great for just about any hunting you are likely to do in the USA other than mayby hign mountain goats and sheep. I am still planning the shotgun SXS to double 45-70 myself. It will be a great boar gun and great for deer or black bear where ranges are usually 100 yrds or less. I have the gun (Belgian hammer sxs), barrel inserts (ace 18 inch chambered sleeves for 12 ga). I only lack the time and some tools or assistance with things I can't really do myself. But, it will come.
I have a nice 1867 dated remington RB in 45-70 sporter. Originally a 11mm Danish RF / CF. The chamber is correct for 45-70. The bore is a little oversize (grooves) but the rifling is so heavy, it seems to accept most .458-.459 bullets or my HB 405 gr cast and shoot them very well.
I assisted a friend in taking a very large 2000 lb plus bison a couple years ago with this rifle. The big lead bullet with a backing of black powder went through the chest, taking out the lower heart and stopped under the hide in the opposite upperfront leg / shoulder. The big old bull just folded. This was after 3 shots from the original hunter's 45-70 marlin shooting 300 gr winchester loads. These were a bit high and the buff went down briefly. When he got up again and started to run, he asked me to give it a plug as I was in a good possition. Excitement over.