My choice for Gemsbok would be the 300 gr. Nosler and I know it will shoot through a buffalo almost every time other than lengthwise and it will come darn close then...

I have no use for lighter bullets than 300 gr. in the 375, if I want better trajectory then I will go to a lesser caliber..The 300 gr will shoot as flat as a 180 gr. 30-06 for all practical purposes and I can reach out and kill a Gemsbok at 300 with the partition..I like heavy bullets on Gemsbok, they are tough animals, and you may need to stick one lengthwise...

Also, my experience is the Nosler is a better bullet than the Swift in killing power, The swift expands into a "smooth" round ball, the Noslers and woodleighs are more ragged in expanded form and tear up more..for what its worth.