Todd1700 said:
"What can this cartridge kill?" then the upper end range on each of those listed goes way up.
Yup the natives in AK have taken humpback whales with 223 Rem. Not recommended under normal circumstances.
Jimbo I think you're looking for the Holy Grail of hunting, everything is so circumstantial, if you're hunting Caribou with a 270 Winchester, and a Moose runs across your path and you have a tag, do you take a Pop at it with the Winny, or leave it since you don't have something bigger? Same goes for everything else.
Personally I'm a fan of bigger is better, good shot placement rules but since we're talking about living breathing and moving critters, a bigger caliber gives you more leeway, even if you can shoot to your rifles limits on the range, out in the field the target isn't at a fixed point with a fixed aspect. If you tag a buffalo with a 22LR in the optimum place (say in the eye and up through the brain-pan) sure you can take it out with the one round, but that's hoping for a lot, if you can do the same shot with a 45-70 and it moves a little well you'll likely take it out just as well, without necessarily the need for more followup shots.
I like my game to be happily eating grass and thinking about humping one second, and not breathing the next. Certainly makes me feel happier by not watching something go limping off, stumbling and then falling over twitching, and having to perform a "coup-de-gras" with my sidearm and have that big confused scared watery eye looking at me (I know I'm anthropomorphizing, so sue me).
That's not to say I shoot squirrels with 50 BMG, although I have blasted a couple with a 12 gauge with 00 Buck, wasn't pretty, "oh look here's a tail...", but I do tend to err on the side of bigger. Just because I could take a Deer with a 223 doesn't mean I will, and I do think that DF&G regs that specify Maximum calibers are totally stupid. However at the same time, I have shot 'yotes with a 22LR ball, 12 gauge and 338 Win Mag hunting round when they were being pests and it was the only gun I had available, but I wouldn't go and hunt them with a 22LR.