303:
The cartridge is at its best on large thin-skinned game. It is a sentimental favourite of many Americans because Roosevelt used it for lion on his African safari, and wrote glowing reports.

It is probably OK on buffalo if a careful shot on an undisturbed animal can be guaranteed, but would be woefully inadequate as a 'stopper' if things didn't go to plan. Boddington brought a Ruger No.1 in that chambering to Australia last year if memory serves, I believe his daughter took a guided buff with it.

Factory-loaded cartridges would be near impossible to get in Australia I suspect, at least within normal price-range. There are many better cartridges for buff, depends on what your intentions are.