firsttimeelkhunter - One suggestion if you go with the 338. Make sure you make the heart or lung shot and not through the shoulders or other areas that you want to keep. Not that it won' t kill the ELK through the shoulders. It definitely will, but just about any meat near the path of the slug will be bloodshot and/or shreaded.
The fellow we stay with in WY and hunt with is big on 338s, because it will kill and/or substantially slow an Elk with even a marginal shot. However, this past year he inadvertantly hit a big cow through one of the rounds on a shot of about 200 yds. where the animal took a step down a ravine going away from him just as he squeezed off the shot. He got the Elk, but most of the round on a hind 1/4 was pretty well ruined.
The other reason he and others in area with dangerous predators like grizzlies carry this is to stop such an animal, if God forbid they have to.
However, there are a number of other magnum calibers and heavy load combinations that you could say the same about, I' m sure. I' m looking at a Tikka Hunter or T3 300 WM for similar reasons and I like the rifle and out of the box accuracy.
Don' t use the 338 on the Whitetails up in MN!