I enjoy your hunt report. Congratulations on that hunt.Old thread but I went to Africa with my .416 rigby in August 2022. I used 400 gr swift A-frame for everything between a frontal shot at buffalo at 35 m and a 212 m shot at a baboon. The only bullet recovered was the one from my sable, under the skin at the far side. So, it is possible to go with a .416 Rigby for do it all but a recommendation is to know the drop for longer shots (which I didn't and hence I missed a truly great sable and had to settle with a good one). I also experimented a lot to find 2 bullets (swift A-frame and barnes banded solids) that produced small groups at the same place. Eventually I found recipies for sub inch groups with centers sub 2" apart but I had to sacrifice speed so they were only travelling 2050 and 2090 fps, but apparently it was enough...
Link to hunt report:
Link
Pretty amazing what a good 400 grain bullet, traveling less than 2100 fps can do on a 1750 pounds plus of tough buffalo.