I'll second the Hornady 150gr SP too. I used that one in the 7.65 Arg. Mauser cartridge and it did the job nicely.
Check the latest Hornady manual for data or the Hogdgon Online Data Center http://data.hodgdon.com/cartridge_load.asp
The data Hogdgon's has listed online is for .308 diameter bullets but is the same if you're using .311/.312 bullets too. As always, start at the min and work up while watching pressure signs.
Have you slugged your bore to determine the actual size? Bore diameter varied in those old beasts and you might be able to use .308 diameter instead.
IIRC, if you search up in the Curios & Relics forum here at TFF there are several threads on what bullets to use with what bore size.