Curl (or whoever the lucky sob is who owns that nice 12b rifle up there at the top of the thread...) could use that double rifle as a coach gun to fend off this tangental hijack of the thread here...

Daryl-

If the flash holes on the barrel tops were slots and not holes, a pinfire cartridge with pins some way up the case wall would work out, not the case with this gun.
Also, the nipples (or whatever firing mechanism) are missing from the gun.
Hence some of the mystery here.

All of the pistol and small-rifle (revolving carbine... essentially pistol ammo) pinfire ammunition I've seen has been rimless. The sporting long guns I've seen and handled (quite a few, some crap and some best-grade work) both rifles and shotguns have all had some provision for rimmed ammunition. I've seen rimless shotshells, although never in the flesh and only in photos of a couple of examples (including the stuff Seyfried has published in his articles), but the rimmed versions have overwhelmingly outnumbered them in the cartridge collections I've seen.

I've come across much detailed text on the numerous metallic/paper cartridges which were fired via percussion through the thin paper case wall, and some of the side-ignition meatllic cartridges which were essentially *internal pinfire* with internal caps and strikers which fired the caps via a blow on the side of the thin metal case.
It's possible that this gun was set up for either.
Hard to tell at this point though.
I thought that if there were some action builder who's 'trade mark' was these action lightening conical funnel thingies like Curl's 12b gun has, there might be a way to look into his history of work for some more clues into what I have here.

--Tinker