Craig--How hard the rifle kicks depends on several things. How much the rifle weighs, how hot is the load, how much does the bullet weigh.
Loaded with a 540 grain bullet and 70 grains of Goex 2f, my 11 pound Sharps kicks about like a 12 guage shotgun with light field loads. It will also shoot completely through a buffalo or bull elk at 800 yards, or any hog that walks. That is the best way I have found to load one.
Loaded with a 340 grain Gould hollowpoint and 70 grains of Goex 3f, recoil from the Sharps is about like a 243, if that much. I feel that bullet is too light for hogs, but it is magic on deer and antelope, not to mention coyotes.
On the other side of the coin, I have a Marlin 1895 in 45-70 that is very accurate with a 400 grain Speer and 50 grains of 3031. It will almost cut a 6 inch diameter bull pine in two with one shot. It will also kick you so hard that you think someone gave it to you to shoot as a cruelty joke. I mean, it really hammers the daylights out of you with that load. I don't shoot this one very much.
Comparing the two rifles and their loads will give you an idea of what is possible. In a 45-70, you can have a rifle that is pleasant to shoot, accurate, and extremely effective on anything you shoot with it. You can also have one that is a real barn burner and no fun at all. It just depends on the rifle and how it is loaded. Shoot straight, rdnck.