I've hunted Oryx at the White Sands Missile Range in New Mexico. IMO they are tougher than elk. You have to shoot thru the front leg to hit the heart. The aim point is -- put your horizontal crosshair on the top of black racing strip on the side--your vertical crosshair right on the front leg. The bullet will take the top of the heart off. Don't shoot behind the shoulder like a deer---you'll miss the vitals. They are more forward in African animals. With this said-----Use a good bullet----Partition or equal. In your case sounds like the "Oryx" load.