I did a hunt like yours in 2011 except that I also shot a bull elephant, a hippo, and a lion.
Ask your PH what he recommends for solids for buffalo. Often they want the first round a soft, then follow-on solids. Mine wanted two softs followed by two solids. He also wanted 300 grain softs for buff. I used North Fork solids and softs. Incidentally the softs slew plains game like the hammer of Thor.
300 grain bullets shoot plenty flat enough for anything you're going to be doing.
I would not bother taking a backup rifle. The PH probably has several in camp. Ask him.
Forget the bangy clangy Harris bipod. When you get ready to shoot, a tracker will shove shooting sticks in front of you. Besides, you'll probably not be shooting from the prone or sitting positions. That's why they call it the LONG grass.
Practice: I used Hornady cup and core bullets. Practice shooting from sticks. Get some bamboo and make your own sticks. I prefer bipods, not tripods, but others differ.
Also practice shooting offhand a lot. You should practice fairly rapid repeat shots, not taking the rifle off your shoulder between shots.Don't waste time very much shooting off the bench trying for tiny groups. 1.5 MOA is better than you need.
As for loads, use Rl 15 powder. Look in the handbook and work up a load that goes 2500 to 2550 fps. The exact last increment of high velocity does not matter.
Scopes: I used a Bushnell Signature series 1.5-6x42. Most people use the Leupy 1.5-5x20. My wider objective lens gives a much better "twilight factor." Besides, I got the LED red dot option. Very useful for shooting lion in the dark.
Make your travel arrangements through Gracey Travel. They have an employee who will meet you at J'burg airport, where you will probably have to overnight anyway, and take you to the hotel, meet you next day, etc.
