DJ Worm-
That .50 cal Ruger sounds like the ultimate. Wow.
I don't think I'm gonna spend the $3500 to get one of my own right now, but if I ever win the lottery it's on the wish list.
If the OP is still around, I agree with the others that a normal B.P. revolver doesn't sound like it will fit the scenario you've laid out. However, what if you used it first? If a group of does walks up 20 feet away, you could shoot the first one with the revolver when you have a calm shot, and then use your rifle after the others pause 50 or 75 yards out.
If you hunt from a stand (or aren't walking too far), another option is to take two rifles. I've done it. Just keep the second one leaned up against a tree or slung on your shoulder ready to go. Heck, 'round here the shops have racks full of used muzzle loaders for $100- you could bring half a dozen of 'em up in the stand if ya wanted to.
If ya just like the revolver, that's cool, but single shot pistols are available in .50, .54, and even .58 caliber. A pair of 'em might be a more effective combo.
In centuries past, a hunting sword, hanger, or Hirschfänger were standard equipment for delivering the coup de grâce. I've finished off plenty of critters with a short sword, and it still works today, with less meat damage than another shot.