Just to follow on from AGW's post, sambar are pretty tough, and are a good size - a lot bigger than your whitetails. The other thing that comes into it in the Australian context at least is that they are usually hunted on public land and like the thick stuff, so the shot opportunities are often more or less fleeting, may not be from a good angle, and you really want the deer down right there or it could disappear into thick blackberry or lantana and be a bugger to find. As well, there are a good number hunted by hound teams, and thus shot on the gallop.

I have little doubt that any of the calibres nominated will do the job, assuming a suitable bullet, angle and placement, so if you can pick your shots on undisturbed animals they'll do fine. I used to know a bloke, now passed on, who shot a large number of them with a .270, but he lived in their habitat and could hunt every day, so could pick his shots.

Personally I have used a .30/06 quite happily, but there is something to be said for something with a bit more bullet weight and diameter for the sort of conditions we hunt them under. A lot of blokes here use .338, 9.3, even .458. This is perhaps especially true of the posted shooters hunting with hounds.