I know this is an old one, but since I have read through it, and actually have been "that" hunter with my 25-06 I felt a need to throw in my .02.
I got a chance to hunt CO the last year out of state over the counter tags were sold. I had several choices available to me with caliber to carry on the trip. I took three rifles since I had no idea of the actual terrain we would be in.
The trip for me and my bud was like being thrown out on a Mars landscape with us being used to E. Texas woods and river bottoms. We went up a week in advance to scout and see what was in store. Of the rifles I took I was VERY accustomed to shoot them all, and in the months preceding the trip spent hours shooting them all at extended ranges to work out the details of drop and such in every available situation I could. The calibers I took were my 25-06 24" Rem BDL, my .270 22" Rem BDL, and my 7mm Rem mag, in a Sendero. I had loaded up the ammo to what I could effectively keep in a 6" zone at 300yds, which with these particular rifles was pretty easily done. THe 25 used the 115gr Partition at 3150, the .270 a 150gr Nosler Solid Base at 2850, and the 7mm a 162gr Hornady moly coated and loaded to 3100fps.
Of the three all were carried out during the week we hunted. THe 25-06 was one I have hunted with for quite a few years and will still easily put 5 shots into a 1" or less group at 200yds day in and day out. It was, of the three, the one I relied on.
In the time spent we had already decided that anything past 300yds was out of the question depending on the area we were hunting, so that in of it's self was one factor. The second was we had to actually find the darned elk. A factor which never came into play unfortunately. The last was IF we found them, how would we go about setting up for the shot. Between the two of us we are both very accomplished hunters and shooters, and pride ourselves on the fact if it bleeds we can find it. We had no intentions even if it was a wold class set of horns of shooting anything we weren't absolutely sure about.
Well I managed to geta nice mule deer out of the trip and we never found the elk. This said, the deer was at a nominal distance of about 30yds at the shot, and when the 115gr Partition hit him, he never moved an inch except straight down and to roll over.
As for the average joe headed to the high country, I am with every post here that says use what your comfortable with. Once your in that arena, your in another world more or less. Flatlanders simply do not have the time to adjust to the atmospheric conditions of going from several hundred feet, or in my case 30 something feet above sea level to anywhere from 4-10K feet above, and finding breathing a viable option. The one fellow in town we spoke with extensively said the best way for us to get aclimized, was to strap on all our hunting gear and hike up there from TX. Even if your a calm collective hunter, when your packing around a 7-9 pound rifle in the high country your going to be breathless when the time for a surprise shot come up. In this time, the least of your worries should be how well you shoot your new rifle, in what ever magnum caliber the internet or big box store salesman said you had to have to kill an elk.
The 25's and the great bullets available today, when put through the vitals will effectively disrupt the breathing and blood pressure just fine. The major issue is putting the shot where it needs to be and not simply shooting AT the animal with your uber magnum that supposedly will knock an elephant off it's feet.
