I have never shot a sambar (never even seen one, for that matter), but I have used a 7X57 on African and American game. I shot two wildebeest in a row using Winchester 174 grain factory loads in my rifle, both one shot kills and both at fairly close range. One was standing, head on, and the other running past me, broadside on, at a good pace, both shot off-hand, with no support. Neither was much more than 100 yards away.

For longer shots I think I would reach for my 7X64 or even 7mm Remington Magnum, but for close shots, and an easy carrying rifle, the 7X57 by all means.