Steve Timm used Nosler 120g Ballistic tips from his .280 AI on Elk with great effectiveness. I'm sure a copper bullet would be even better.

I have used the 120g. GMX from my .260 on several Montana Muleys and would have no problem shooting an Elk if the opportunity presented.

The only word of caution is that the mono's can over-penetrate. Be aware of what is behind the Elk (such as another Elk). If you shoot the shoulders at a right angle, you are likely to destroy both shoulders.