During this snowstorm & minus 14 degree F temperatures, I’m not spending much time in the shop as the ductless heater is not keeping up.
I’ve attached a photo of a Hepburn I purchased at the last November Tulsa show. The chamber cast shows it unlike anything I’ve seen before. The groove diameter is .315 and should work as a 32-40, but obviously the chamber is not a 32-40. Almost seems to be a reverse of Pope’s 33-47. I knew this when I bought it so paid accordingly. What do you think this could be? I’ve looked thru the World of Cartridges and haven’t seen anything that it might be. If all else fails I’ll have it lined, but thought I’d try here first.

I agree on the COTW as not being gospel, but hoped I might see something similar. A number of cartridges in it don’t give any measurements so can’t tell what they look like. This is an extremely tapered case compared to the 32-40 case. Also the original barrel is stamped 32-40 so assuming that is was originally and it doesn’t appear rebored, except for the chamber cut.

Looks darn close to me.

SBoomer,
I saw that .32 Remington, it is pretty close, except it has a slight shoulder. I wonder if the chamber would be for a fire formed .32 Remington. The cast is a tapered straight wall. I think I have 43 different cartridges sizes, but no .32 Remington! LoL 

Correction— I thought it was a .32 Remington,but it’s not, it’s a 32-40 Remington. Was not aware of that cartridge and a photo I just looked at is very similar to my cast. If it’s as close as my first look at it I may have to buy some.

Here Richard, this might help, in addition to what the others have said..in a lot of ways.  From the Handloader's Manual of Cartridge conversion book.
Bob

Richard, it’s nice to have on the shelf.  Won’t say it has all the old cartridges, but it has most in the 600 plus pages.
Bob

That’s a pretty big groove diameter for the 32-40 Rem Hepburn but that’s what you appear to have. I have been working with a Match B in that caliber and it measures .309. After forming brass from .303 British I have to inside neck ream in order to have clearance in chamber for fixed ammo.

JMH,
Sounds like a fun project— I’m always a sucker for fun projects! Really enjoy bringing them back to original calibers and configuration. Although I do like the famous gunsmiths of old who did great work. Good luck on your Hepburn, would like to see photos of it when you’re done reconfiguring it.