I kind of agree with OldFart. I really think you should carry as much gun as you can accurately shoot, and a gun that matches your "conditions". 30 caliber guns are a good "all around gun" for elk. Will you be hunting blowover? Open plains? Most of my elk have been killed at 300 yards or more.
An elk is a big animal, and I have seen on multiple occasions, an elk take a killing shot and walk off like nothing happened. Also, elk have a big chest cavity, and sometimes don't leave much of a blood trail at all. Its difficult trying to track your elk you shot at, as it follows a herd of elk.
I use a 300 WSM with Barnes 168g TTX
I've shot 2 diff elk thru the lungs and had them run probably 300-400 yards before piling up.
I shot one elk 4 times @ 400 yds, and it just stood there like nothing happened. 1 shoulder shot, 3 chest area shots.
Every other elk I've shot has dropped or only taken a step or two (10 - 12 elk).