Help me pick my elk hunting caliber

what calibers do you currently own?

Those are all overboard in my opinion.

.300 mag is more than enough.

300 Short Mag would be my choice.

I hunt elk with 338 win mag.

All of the above are great choices, and more than you will need. I do not feel that any of them are significantly better than the other, get what you like, but most important is to shoot it as much as you can and know what you can do with it

I have the .338 win mag, have not shot an animal with it yet, but have it dialed in pretty good (1 1/4" group @ 200 yards) with a 210 grain bullet

Whatever you use for deer. Unless you want to go buy a new rifle, then get whatever you like the most, they will probably all do the job equally well. People kill elk with .243s every year.

I bought a 300 WSM Weatherby mark 5 so I could hunt elk once a year when we have a family gathering in northern New Mexico and still be able to hunt white tails down here. Works great.

Same reason I'm buying one.

The .338 would destroy a deer.

The OB sponsored cartridge, two fawty tree Winn chester

I currently own two large game rifle calibers: 30-06 and .280

I gave the 3 choices in the OP because my friend that is the PH recommended them. He said any of the 3 will do, but be prepared to shoot 300-350 yards for a good bull.

I've heard the stories-.243's, .270's, .308's, 30-06, etc. kill elk every year. But I plan on buying a new (used) gun (or building one from a Mauser receiver I have), and am looking for suggestions from those that have shot the 3 calibers suggested, particularly in anger at a Wapiti.

As for the .300 WSM-I've never really bought into the WSM mags. In comparable barrels, their ballistics fall between the non-magnum calibers and the true magnum calibers. If I'm going to step up, it's going to be a real step up from my 30-06 and .280. To that end, I asked the PH about a .375 H&H in case an Africa or Alaskan brown bear trip were in the future, and he said that would be fine on elk shooting 260 gr., but would suggest something a little flatter shooting with a better BC and SD. Thus, the .338 cal. mags.

Rifle weight is not really an issue, as long as it's at or under 8.5 lbs. with a scope, which is fairly easy to achieve in a lot of rifles these days.