Here's an article about the .270 WSM.
I've shot a Rem .270 for over 30 years. 6 Elk, 8 Mule Deer and countless Antelope; that .270 delivers.
To listen to someone tell you, "it will bounce off" is, I hope being sarcastic.
What you really need to know is no matter what caliber you shoot, will there be enough kinetic energy on target at the distance you're shooting. I taught hunter Ed in Colorado. Certainly Elk country. Their DOW (Fish & Game), says you need a minimum of 1000 ft lbs of energy to humanity dispatch a big animal such as an Elk.
So when I built my reloads, I clocked the bullets via a chrony and used my Sierra load data to help approximate energy out to maximum distances. My bullet of choice was the Sierra 140 BTSP. I ran it at slightly under 2900 fps. It was so accurate the gun shot .323 groups at 100 yds.
A 150 grain in .277 moving at say 3,000 fps is a formidable killing agent when delivered with pin point precision.
Sure you might hit a Bull at 600 yards, but if the energy loss at that distance falls below that 1000 ft lb threshold, it's a wounded or worse, lost animal.
I've never failed at harvesting an animal using that 1000 ft lb energy mark.
And by the way, Colorado minimum caliber for Elk is a .243. I knew an entire family of guys who ran a game meat cutting service.
Everyone of those guys were capable of head shots at over 300 yards. The caliber of choice for them was the .243.