This thread will no doubt bring forth various suggestions from many hunters, all promoting their favorite .375 "soft."
I will only note that the most experienced African PH I have hunted with prefers his .375 H&H when backing up buffalo hunters, reserving his .458 Lott for elephant guiding. I asked him what expanding bullet he prefers in the .375 (and his preference is for expanding bullets) and he said, "Whatever my clients leave behind. Today they're all good."
This guy has been either a game ranger or PH for over 40 years now, and has personally killed over 600 buffalo, so I listen when he talks.
