The 1940 RWS Handbook has 2 loads, both with a 12.7 g bullet (note these are .318 diameter bullets). Powder is "T 1910", obsolete.
First load with 1.8 g powder has muzzle velocity of 533 m/s, pressure is 1800 at (atmospheres).
Second load with 2 g powder has v0 = 581 m/s, pressure 2000 at.
The modern RWS reloading manual (edition 9, 2002) gives loads for several current RWS powders, again with a 12.7 g round nose bullet from RWS.
Velocity range from min. 520 m/s to max. 575 m/s. They use powders of medium to slow burn rate (R 902, R 903, R 907, R 904).
I hope this will help.
Fuhrmann
