I just went back to your original post and saw where you said
SLOW MOVING large bore. Well, the 45-70 barrel becomes even more attractive.
A friend of the guy who just built the chest-rig for my .44 RedHawk, out in Montana, just shot a young bison (about 1000lbs) clean through the shoulders with a 419gr. wide-flat-nose cast bullet at only 1200fps!!! It was actually a ranch and, the rancher allows you to kill your own buffalo if you wish. The friend wanted to use the 300 win mag of another "hunter"
.
The rancher took him aside and suggested he shoot it with the leather guy's 45-70. I know as well as you that the 300 win mag would've got the job done. But, the rancher convinced him and, it worked. The animal acted as though he'd been shot with a BB gun, took two steps, quivered a little, and keeled right over!
There really is no need to punish the shoulder if this kind of performance can be had at 1200fps. I will never need more penetration than needed for a 1000 pound bison! Making me rethink my future reloads for sure. Wes Daems, the leather guy, says he can shoot these loads all day with no ill effects.