Back in '81 while I was staying with a friend in West Germany we were loading for his little Belgium double hammer gun with 24" barrels chambered for the 10.75x47 cartridge. We swaged 265gr 44cal Hornady bullets from .429" to .423".
From memory we got reasonable accuracy and regulation with the load we finally settled on.
My friend eventually immigrated to NZ and my notes taken back in 1988 show our load as being 45.0grs of Rottweil R902 with a RWS primer in original cases with the Mauser A base head. Chronographed MV of this load was 1588fps.