Dear Ralph,
At the every step I became more and more sure, that we have barrels of the same caliber and for the same cartridge.

I wanted to illustrate my post with a couple of photos, but my image-hosting are not working today. I will do it as soon as possible

I have asked you about rifling shape and number of lands because sometimes it is possible to find left and odd rifling (so called Henry). It is very rare in drillings.

A am planning make the experiments with casts bullets too.
Are You speaking about this website?
http://www.ranchdogmolds.com/

Double rifle drilling is a very rear weapon. Such gun is very interesting ever.
Who may be the gunmaker of Your gun?
How do You think? When it may be produced?.

Sorry for my English. I know that my grammar is terrible. Is it more or less understandable? If I will wrote something too difficult for understanding, please don’t hasetate and ask a questions.
Sincerely Yours
Oleg