Will this set up kill as well as the 45-70 ?
It will also bruise your shoulder just as well
They tend to be less accurate than the .45-70. The recoil with factory ammo kills scopes pretty fast. One that will hold up is the Nikon Prostaff 2-7X32.
They tend to be less accurate than the .45-70.
When did you discover this?
When they first became avaliable. The .45-70s typically group about the same at 100 yards as the .500S&W will at 50.
I don't own nor have I used a 45-70 for hunting. However, I have used the H&R 500 S&W rifle for deer hunting. I don't yet reload for it but the only factory load I've tried (Federal with the 275 gr Barnes XPB bullet) is very accurate at 100 yards and has done a number on 2 deer that I've shot with this combination. Also, this load does not (at least to me) have significant recoil. You can of course get factory ammo or reload ammo in this caliber that'll kick right smartly. One of the deer I hit was about 80 yards away and I only had a couple of seconds to shoot. Though I hit the deer low in the stomach, it didn't go far before dropping.
The downside to this caliber is that, if you don't reload, prepare to take out a loan to do any appreciable amount of shooting. Most of the factory loads (especially the Federal load I use) are expensive.