Our antelope killing has been with .243, 6mm-06, .257AI, and 7mm-08. All work for the purpose. In my mind something in the 6mm class shooting a bullet with a decent BC is hard to beat if purpose building/selecting an "antelope" rifle.

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

One nice thing about antelope is they tend to be a fair weather adventure in open country so if you are partial to fancy wood and deep blue finishes you can probably use that type of rifle fairly regular.