Purchased this roller a few weeks back from a good friend. It has double extractors and a fairly tapered case that fits a bore size of .470 that reduces down to around .462 at the muzzle. The bore is very bright and the rifle show no signs of being shot with black powder. 

I have several questions about forming brass for the rifle and load data. I am currently cutting down and sizing 470 Nitro cases to make the brass. Based on the chamber cast the case is 2.750 long or at least that's what seems to fit the chamber.

Any original load information for this cartridge would be really helpful. Getting ready to order some bullets to fire form some cases. I have a 458 molld that will drop a .462 bullets that I thought about wrapping some paper around and using to fire form the cases. I just don't have a warm fuzzy feeling about this cartridge enough to start dumping 2400 and COW in the case pushing a 350+gr bullet down the bore. I have done a lot of testing using a RSI Pressure Trace system with a Carl Gustov 8x58RD roller so I know 28,000 PSI is whats safe. There just is no data on the comercial rollers that I know about. I have no idea when this rifle was made.

Smokepole50

That's interesting and would be a great story of how that rifle ended up in that cartridge. I have one in a Westley Richards. It has the original slow twist that these express rifles used for light bullets at high velocities. I've chronoed mine at over 1900 fps with a 300 grain bullet. What is the twist on yours? Hopefully it is faster so you can use heavier bullets. Have they used an original Martini Henry barrel? Does it have Henry rifling? The bore dimensions sound like it. If so you might try the hollow based 405 grain bullet.

Thanks for the ideas guys. Dug out my old .490 RB mold and ordered some .457 sizing dies to open up to the correct size.

double extractors........I've been told that's rare.