This is what appears on the Namibian Professional Hunting Assoc.'s site:
"Smallest calibre 7 mm.
Minimum energy (Eo - muzzle velocity): 1350 Joule for springbuck, duiker etc.
2700 Joule for hartebeest, wildebeest, kudu, gemsbuck, eland etc.
5400 Joule for buffalo, elephant, rhino etc."

Per Norma, the factory 286gr bullet at 720 meters per second [2362fps] has 4795 Joule [3536ft. lbs].

I think Zimbabwe is the one country that requires 9.3 (.366) or bigger for dangerous game. Most others require 375. Tanzania is one place I wouldn't take a chance, the game scouts can and do show up. If you are on private property (ie a fenced ranch) you can do whatever the PH lets you do.