I've taken one bull and one cow each of gemsbok "on license" or however you say it plus, one gimpy bull culled, all three in Namibia, 13 or 14 years ago.
These I shot with a '98 Mauser in .300 H&H / 180 grain Nosler Partition, at just a little over 2800 feet per second - extremely accurate.
The cull shot was a bit over 400 meters/yards, according to the PH's Leica range finding binoculars.
He was facing us and my bullet struck at the juncture of throat and brisket, he dropped to the shot and was quite finished before we got to him.
The other two were somewhat closer, but at this stage, I do not recall their specific distances.
That culled bull was one of the very few spent projectiles that I was able to recover on that hunting trip, as most of the others passed clear through most animals / species I shot.
This cartridge and bullet combination worked so well for me that, I would merrily use same again for gemsbok and / or similar sized game in any open areas, where somewhat longer shots are common.
And although I would prefer a bit more bullet weight if I was hunting 2,000 pound eland, nonetheless I wouldn't be too surprised if this combination can cleanly bag an eland (of course presuming proper shot placement).
The .300 H&H is usually over-looked by hunters today, but this is a mistake, as it seems to have that strange property of remaining accurate, almost no matter what you feed it (the .222 Remington is another one like that IMO).
The original H&H version feeds and ejects smoothly, due to it's slow tapered shape and burns less powder than the other .30 magnums.
The others (various "younger" .300 Magnums) that followed it's introduction (1920 ?) don't make anything "more dead", they just kick harder and make more noise.
El Finito:
Admittedly, the Swift A-Frame is a tougher bullet than the Noslers are and, I believe it (A-Frame) is the best of the best premium softs however, the good old Nosler Partition is still a very fine "Plains game" bullet, one of the better choices, even after all these years.