I don't know what's available in Australia, but I have used 42 grains IMR 4895 with 270 grain RN.
For brass I have used .35 Whelen with excellent results.

I worked that load after lengthy (pre internet) research some while back and it nearly matches the recommended load stamped on my M1910 for Cordite (9.5 M/M EX Cordite 43-270 MAX) along with its Birmingham proofs.

I have posted the "Ballistics of German DWM Cartridges 1935" pages of the 1939 Stoeger catalog on TheFirearmsForum.

I'd post them here, but every attempt I've made to post images to this site has ended in frustration.

From the 1935 chart, the load for DWM 531 was:
Case - (DWM) 531
Bullet- (DWM) 407A Soft nosed round head
Length- 28mm
Weight- 17.6 gram (271.61 grain)
Powder- 3.25 gram
Powder- R5 (Rotweil smokeless rifle leaf powder #5) 3.25 grams would be 50.15 grains... ouch!
V25 m/s - 627
E25 kgm - 354
Pressure kg/cm2 - 2600
Barrel Length - 60 cm