So far, here's the tally:
1 vote: 280, 284, 30 Nosler, 300 PRC, 338, 264 Wby Mag.
2 votes: 28 Nos, 270, 6.5 PRC, 300 WSM.
3 votes: 308
7 votes: 7mm Mag, 300 WM (includes my vote!)
8 votes: 300 RUM
0 votes: 30-06 (just had to throw that in there!)
Based on this, the 7mm, 300 WM, and 300 RUM are very popular for mule deer and elk. True, a lot of elk are taken with other (oh wait, should I say caliber? or cartridge?
- OK I'll just say guns!) guns. But when you compare the ballistics of those to many of the others, they are very similar. Sure, as far as energy, there is a big difference in the 308 at the bottom and the 300 RUM at the top, but there are lots of steps in between.
Really it comes down to personal preference, specifically, how much are you willing to pay for ammo? what kind of bullet selection do you have? Factory ammo or reload? how much recoil can you handle? How much are you going to practice at 800 yards? After about 350 yards, bullet drop is exponential. If you're estimating 50 yards off at 200, likely no big deal. But between 750 and 800? You better know your range and have some good ballistics info and knowledge. For me, 400 yards is tops. Won't shoot beyond that.
20 years ago, I was in your situation - looking for an all-around gun for eastern whitetails, as well as 400 yard shots on antelope, mule deer, and occasionally elk. I went with the 7mm Mag. It has served me well. In hindsight, I wish I would have gone with the 300 WM (I inherited one since then.) for my occasional elk hunt, and then picked up something smaller like a 270 for the eastern whitetails or antelope.
So, my advice, go to the range with friends. Shoot different guns and determine your recoil tolerance. The 300 ups (WM, RUM, Wby Mag, etc) are going to pack a recoil punch if you're not used to it. The 270', 7mm, 284's are going to be less. I'm not familiar with the Nosler and PRC's.
Forgot to mention, there are quite a few responses from some very successful hunters on here. If you stick around long enough, you'll see who they are. Not calling any names because then someone will get ticked off that I didn't name them and they've killed 28 elk out to 1000 yards and someone I named has only killed 16!
This was longer than expected, but hope it helps.