How? Not by reading books and internet forums. I've used everything from the .243 (the legal minimum in most western states) through the .25-06, .30-30, .308, .30-06, 7mm Mag, 7mm STW, .300 Win Mag, .300 Wby Mag, .35 Remington, .375 H&H, and .44 Mag on animals ranging from pronghorns and deer through caribou and elk. Though all will work, some work decidedly better than others, depending on the animal - and depending on the ranges at which the animals are typically encountered.

I did not suggest that the .270 is inadequate for elk. It's limited in what bullet weights are available, the heaviest being 150-grain. 150 is the lightest thing I'd reasonably throw at an elk, given a choice. My experiences are simply my experiences, though. Take them or leave them.