DesertMuleDeer,
What everybody else said, especially about shooting through one buffalo and possibly wounding another.
Plus the fact that, in my experience, the theory that marginal bullet stabilization has much if anything to do with what happens AFTER a bullet expands is pretty much BS. At that point all bullets become less stable, and how well they track and resist tumbling has more to so with the length of the shank and diameter of the "mushroom" than twist rate.
A bullet like a TSX with a relatively small mushroom area compared to the shank will tend to be more stable than a bullet that expands very widely and leaves little shank. But they ALL can tumble, depending on what they hit--and the angle they hit it.
Yeah, the 400 TSX's stability is "marginal" in a 16.5 twist, but it's on the right side of the margin. But as somebody else mentioned, why not use the 350 TSX? Generally TSX's (and other monolithics) are more effective on game when lighter bullets are shot at higher velocities. The exception would be when shooting at longer ranges, but that's not a factor here.
I can also assure you, from personal experience, that a 400-grain Nosler Partition or Trophy Bonded works fine from a .416 Rigby CZ.
