I have a Mauser 1930 catalog reprint and it lists the velocity of the .318 Westley Richards with a 250 gr bullet as 2230fps out of a 23.6" (600 mm) barrel. The brand of ammunition is not given.

Interestingly, Woodleigh's catalog states that 2250 fps is attainable with their 250 gr bullet out of the 8x57JS.

-Bob F.