ORIGINAL: hightopoutfitter
A .270 with a good weight retention bullet above .430 bc, 130 grains or heavier with good shot placement will put an elk down all day at 600 yards above 6000 feet elevation. Its all about practice and your abilities behind the gun. Practice, practice, practice. Take a good shot. Ethical choice, good rest and you will be fine. I wish you the best.
I hunt in the Rockies for elk every year and I'd say about 99% to 100%of the hunters I've met are cable of making a 600 yard shot on elk with a .270. They didn't practice much out past 100 yards, but they zeroed in 3 inches high at 100 yards, and they stayed at a Holiday Inn last night. What a crock of poo poo!
Even a great factory round is probably going to have a drop of4 1/2to 6 feet at 600 yards. When you are measuring the drop in feet instead of inches, there are only a handfull of guys that can make that shot on a regular basis. Not a single one of them are in our elk camp, and we hunt with some elk killing dudes. (including myself)