Mike,
I am somewhat cautious because my rifle was made before 1912. I think that the proof marks indicate that it was proofed as a black powder rifle. Therefore I am pursuing NfB loads.
Reading Graeme Wright's "Shooting the British Double Rifle", he lists a load for the 360 EX (BPE) of 25 gr R7 with a 190gr jacket bullet for 1700 fps. The 9x58.5r Sauer and the 360 EX are almost identical so I will try that load.
The only reason why I am looking for a little more velocity is that, with my initial load of 22 gr IMR 4198, the right barrel shot slightly right of the left barrel, indicating I needed a quicker bullet.
