I know bugger all about Sambar except that they are big! While I have no doubt the 30-06 and various 7mm will work, have you considered a 9.3x62? It is an excellent round which would cope with anything you might want to hunt in Oz as far as big game goes. You can get it in a CZ550 American at a very reasonable price and i bet it would have better felt recoil than that 338 Tikka too..,.

Regards,

Pete