I imagine a 300, 350 or 400gr would work out of 416. I would personally lean towards the 350 as extra speed never hurts a TSX, and it would flatten trajectory out if you needed to stretch it for PG. Dedicated buffalo hunt, a 400gr would be my choice.
My 400gr .423 worked fine last year on my buffalo, right at 2200 fps and the shot was a whole 40 meters long.
