remarkable problem, could indicate the rifle was made for the DWM 10 gramm softpoint load

I think this is the round

the 15,6 gramm roundnose bullet is a good idea on big game up the 150 meter but as a moutain rifle on chamois maybe not the best. could be the rifle was ordered just to shoot this load.
maybe its possible to load the post war Kynoch cartridge because this roundnose is longer and more "spitzer".

Kynoch, DWM, bulgarian surplus