I have hunted with a 358 Win and the Whelan has about 100 fps advantage. I now have a 9.3X62 with 24 inch barrel & this has a slightly bigger advantage over the Whelan & with heavier bullets.

In the real world, my 9.3 is probably as good as a Whelan for Sambar or less. It is probably a better performer on Buffalo (I have not hunted them).

If I was after buffalo, I would go with an Ackley Improved chamber as suggested by Jabbali hunter. If it is for general hunting, I would stick to the Whelan. The value of the rifle would be retained if it is a Remington Classic (each year they bring out a differnt caliber).

Good luck