I have shot a few animals with the x bullet.
Took a heavy buck antelope with a 7mag and a 140gr x bullet at appx. 400 yards.
One shot flipped it over and that was it. Maybe a little to much power but it was very dead. Pencil hole going in and golf ball hole going out.

Large bodied muley buck at 30 yards with 130gr x bullet in a .280, pencil sized hole going in and golf ball hole going out. Deer traveled 20 yards.

5 point bull 7mag, 175 gr x bullet, shot facing me through the neck and spine and back between the shoulders and upper chest and exited in front of the rear quarter, he did not take another step. Pencil hole in pencil hole out. He needed a coup de grace from a couple feet, went in through the lower chest and out through the upper chest on the other side, pencil in pencil out.

I won' t bore you with details of any more but you get the idea, I have seen very consistent performance with the x bullet.
At 308 velocities it would be hard to beat for big whitetails. On smaller variety whitetails I would choose something with more expansion.

Rangerlab,
One bullet I would not recommend for antelope is the ballistic tip in 7mag. It will ruin the whole front of the animal, been there done that.
You don' t need much penetration on an antelope but you don' t want to blow it up either. The 140 x bullet sure worked well for me in 7mag.
More important with antelope is to find the most accurate bullet and practice with it at long ranges.