Brass for any of the English calibres is easy to get, especially 404 and 416 Rigby.

I would suggest going 375H&H - it will give you a larger bore size and can handle anything
on the planet you will hunt (if need be !!!).

It is more than capable in handling buffalo. It is also better to learn to shoot a slightly smaller
calibre well (if you can call 375H&H small) and get good shot placement than shoot a larger
calibre badly - and the 458H&H does kick alot more than 375H&H.

Brass, ammo etc etc are alot more readily available and factory ammo is alot cheaper.

Hope this helps.

500 Nitro