[clif]

I have hunted and killed antelope in New Mexico with everything from a .243, 6/284, 280AI, 300 jarrett, and 308 Baer. The shots are generally 250-450 yards. First off, antelope are not very sturdy, so they are easy to kill, even with a slightly misplaced shot. The .243 bullets will do the job up close, but I would not want to bet on them out to 500 yards. I would pick which ever of the 7 or 300's is the most accurate and you are most comfortable shooting with. Remember too, the bigger you go, the more recoil there will be. When shooting at this distance, chances are you could be firing your gun alot . I would also pick a lighter bullet to reduce recoil. I also found that a Harris bipod and/or shooting sticks are a must on these hunts.
Good luck