Well my first choice is still my last choice.

The .318 Westley Richards. One of WDM Bell's favourite rounds and a great killer of game in Africa.

From the Westley Richards website:

.318 Westley Richards

250 grain Soft Nose or Solid Bullet
Muzzle Velocity 2400 ft/sec Energy 3200 ft/lbs BL 26"

Woodleigh makes a 250 gr RNSP Weldcore and FMJ, and Bertram makes a 180 gr SP, and 250 gr soft point at a cheaper price. Maybe some .338 bullets can be swaged down as well.

Brass can be made from .30-06 brass.

I like the 8x68S, .338/06, .318 WR, .333 Jeffrey range of cartridges for medium game, and the .318 is also a classic.

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Gentlemen, however please update this thread as you might read different Indian hunting books. I am more than interested in recording what calibres were predominantly in use in India. Thanks.