Regarding the 30 caliber rounds, both the .308 and .30-06 can shoot bullets up to 250 grains (heaviest made as far as I know); it's been done before. Both those really heavy bullets have been used in competition at 1000 yards from both cartridges with stellar performance accuracy wise. And a 250-gr. hunting bullet would do well on very big game from either case.
Accuracy wise, the .308's king of the hill. For hunting game up to big deer, the .270's a good king of that hill. For larger game up to moose and elk, the .30-06 is the best of the three.
That aside, the older, weaker .30-30 WCF and .30-40 Krag's been used on everything from Kodiak bear down to mice; kill's 'em all dead with the first, well placed, shot.
Note that game's killed with bullets, not cartridges; nor rifles, either, for that matter. Pick the bullet caliber, weight and type you want to use, then pick the case you want to shoot it out of. How fast that bullet leaves determines the maximum range you should use it on game. There's no way one can tell what cartridge nor rifle fired a given bullet entering the vitals of a game animal at 1947 fps doing all the right stuff to put it down instantly from just an autopsy of the animal.
I suppose a 50 caliber BMG round could be held in ones hand and stabbed into the brain of a deer, but that's a rather risky way to kill a deer with a cartridge. It would be feasable to stand back a couple of feet and hold your rifle by its barrel then swing it such to smack the deer up side its head with the buttstock; a good way to kill one with a rifle.
Last edited by Bart B.; September 27, 2012 at 12:06 PM.