IF it is a 10.5 X 47R, I've been loading that cartridge for 10-12 years. It is just about the equivalent of our 40-82 WCF. I think it's a pretty good little cartridge, if a bit different from what we're used to. All the X47R cases are based on the 11.15 X 60R case and you'll probably have to make your cases using it as a donor. Graf's USED to have some Bertram 9 X 47R cases that could simply be necked up, IF they're still available. Supposedly an Austrian gunsmith by the name of Stahl was the developer of the 47R cases. CH-4D used to carry the loading dies. Mine are from CH-4D. It should be a fairly old firearm. Is it Nitro proofed or, even proofed at all?

My 10.5 is in a combination gun so there was no challenges with regulation. I also have a pre-1893 proof law double in 11.15 X 60R. I had to lightly duplex a load to get it to regulate. That load hovers between 2 1/2 & 3 inches at 50 yards. It also shoots cleaner than some smokeless loads I have.