I am pretty sure Holland & Holland were the ones who starting making 12-bore rifles regulated for the 9 dram load of black powder. They first show it in their 1887 catalog. So yes there were 12-bore rifles regulated for a 9 dram load. I believe other makers made a few rifles using this load too, as I have also seen a 12-Bore Tolley that is supposedly regulated for 9 drams of black.