SES,
You are experienced enough to not let the recoil sissies and inexperienced 1886 shooters dissuade you from having fun with your new rifle. It likely weighs a bit less than my 1886 with 26 inch barrel, but mounted properly, it will be fun to shoot.
One interesting thing that I discovered was that even a 300 grain .458 bullet is big medicine for most thin skinned game from deer up through Nilgai and leopard. For Bison, Cape Buff, and ele, you will need 400 grain and up bullets of appropriate construction. A 450 grain Kodiak FMJ at 2150 fps does recoil a bit, but it is very effective on big bad critters.
Good hunting.