As Jeff Cooper once said "What do you want it for?"

400 Nitro and Capt Curl are correct.

The best calibre for the double rifle hunter under 40 cal iks the 9,3x74R.

Brass, and bullets are easy to get.
The 9,3 doubles are ab olut one half the price of 375 doubles.

They are lighter, sleeker, handier, and kill just as well as the 375 doubles.

I have killed a lot of game with my 9,3x74R Chapuis double,
from bobcats to elephants it has performed PERFECTLY.

It is the ideal double under 40 cal.

PERFECT in EVERY WAY.