Thanks to Carignan 577, Alyeska 338, Ribbonstone, and Jack Monteith for their fast and most helpful responses. I have decided to make a chamber cast to get to the bottom of the cartridge dimension questions before I do anything else.

If the dimensions turn out to be the same as the old-old stuff that I have, then these cartridges can head into someone's old cartridge collection.

If the dimensions are for some other cartridge, then I'll find it, have it made, or make it myself. At any rate I won't be shooting anything older than I am.

This has been some education! I've never reloaded anything, but this might be the time to start doing it. Im sure I'll be back on the forum on this same subject as things start to unfold. Thanks again fellas and thanks to 'Shooters Forum' for having such a great place to post questions.

Keep us updated on what you find out. There's a few folks here that load Black Powder Cartridges, if you have any questions after finding out exactly what you have.

Good luck