Sorry bud, thanks for clarifying, we can't rule out the lowest common denominator around these parts.
The 30-06 cartridge, sure, it's capable. But only if you have the right impact velocity, the right bullet, the right wind/drop dope, and the right shot placement.
Now the same can be said for any option we talk about here. It's just that the 30-06 has a smaller window of capability than some of the louder options. Or put differently, it's harder to use for that particular application than some of the louder options. It wouldn't be my first choice. But a 400yd shot on an elk wouldn't be my preference, either.
400 yards is a chip shot for a 30-06. Since when is a 165 grain 30 caliber bullet with a muzzle velocity of 2800-2900 fps marginal at that distance on Elk?