It is all about shot placement. If you hit him in the rump -- good luck.
I used 150gr 308 for my elk.
Also 150gr 270 for my moose.
No problems with either.
If you have buck/elk fever, maybe a bigger gun is what you should use.
Basically, you want some velocity and some foot-pounds when you shoot at an elk.
And you should be able to hit what you are aiming at.
Good luck if you are shooting at an elk running at 30 mph across a canyon.
Fancy custom loads, rifles and scopes won't help if you are a poor shot.
Look at an elk archery target. It will give you a good idea as to where to aim.
Have you tried having a buddy stand behind you and yell while you are aiming at the range?
Good concentration takes practice.