Fella's;
Oh, good grief! Followed by; Bah and Humbug!
The 7mm/08 will do just fine, practice with it.
You do not need heavy bullets to make the ought-6 effective beyond 400 yards.
Antelope are plentiful in Wyoming, lived there for decades & got mine damn near every year. Then I moved to Montana, there's a few here too. If you have to shoot more than three hundred yards to getcher goat in Wyoming you aren't hunting correctly.
The longest shot I've taken an antelope with was in Montana. The gun was a Winchester model 70, .30-06. The bullet was 150 grains and it entered the animal about 2 inches from exactly where I wanted it to. I wanted to hit the spine just in front of the shoulder. Instead it went in just under the spine & just in front of the shoulder. That made no difference, he was rolled over D-E-D when I recovered from recoil. There was a good breeze (Rocky Mountain front range winds) coming over my left shoulder when the shot was made. The laser confirmed range was 470 yards. The scope was a 10X max power with normal crosshairs. However, I did know the gun, the load, the game, and the territory.
900F