I have a 20" Katahdin barrel in 45 70. It makes for one very handy rifle in that it is short and realy light. I think mine is only about 7.5 pounds with a small scope on it.
Mine has a Limbsaver recoil pad to preserve my shoulder.
405 grain buffalo rounds using black powder are very acceptable. You could shoot them all day. I have not tried anything else through it yet.
I had a .450 Marlin Barrel from which I shot the Hornady factory rounds with a 350 grain bullet at over 2000 fps. That will get your attention and I could never shoot more than about 15 of them at a sitting.
There are a couple of boxes of Leverevolution ammo waiting to be fired from my 45 70, just have not had the chance to try it yet. But I am sure it will be similar to the .450 marlin factory hornady.