I would have no issues using Marshal's bullets on buff, hippo, lion or leopard............I would go for a heavy for caliber and not drive the snot out of it and I believe they would work 100%. A 320 gn from a 375 at about 23-2400 would kill buff just fine, devastating energy transfer and I believe you would get great penetration..........I got decent penetration, about 2 ft on the grizzly this fall in a worst case scenario, 30 mtrs or less, a med weight 270 gn 366 bullet, muzzle velocity over 3000 fps, impact velocity over 3000 fps.........over 1" expanded bullet weighing 258 grns........where's the down side. Now what if that were a 300 gn bullet at even 2700 fps, it would have gone through that bear and another one if they were stacked up, I have no doubt what so ever.
You know DL there's only one way to find out............Oz next August? I'll use the Matrix in my new 378 Wby and you back me up with some A-frames or something. Actually I think I'd rather use the 375 Wby with 320s about 2600 fps........just gotta talk Marshal into making me some 320 semi round nose, flat base bullets in 375..............He's already made me some 285 gn RBTs, I would try them too, at about 2950-3000 fps just for giggles, I think they would be devastating on broad side shoulder shots.......