I have used my Alex Henry circa 1873 with Damascus barrels and NFB loads in a 450-400 x 2&3/8 for big eastern whitetail
Deer up here eastern Canada. I use a 200 grain .410” cast bullet at 1850 feet. It would be somewhat similar to hunting with a .41 magnum revolver I suppose. Broad side shots are what I look for but it is effective. They don’t bang/flop but they do get dead after running for a bit like a scalded cat.