Doc Ivory,
The books mentioned and listed in posts #2 and #3 above are all good references. I believe I can add a little to the list, though.
I think it is safe to say that trade guns in North America were intended
primarily for distribution to the native people. In learning about the guns, it's good to learn how they were accepted and used by, and how they affected native people. With this in mind, another book I would strongly recommend is
Gifts from the Thunder Beings, by Roland Bohr:
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You did say you were most interested in Northwest Guns, but in considering these, it is also good to think about their antecedents. For an excellent and scholarly treatment of earlier trade guns, especially those from France and Britain, it is hard to beat T.M. Hamilton's
Colonial Frontier Guns. The title is somewhat misleading. This book is about trade guns.
The journals of the American Society of Arms Collectors (ASAC) are a trove of information. Lee Burke wrote an excellent monograph on early English trade guns, or "Carolina Guns." These were the direct ancestors of Northwest guns. Here is a link to the article:
Carolina Guns
Charles Hanson (author of
The Northwest Gun, mentioned in post #3) wrote a fine monograph on Northwest guns for the same journal:
Indian Trade Guns
Hanson's article gives a very neat and concise history of these weapons.
There are a couple of additional articles that should be of interest, in the
Canadian Journal of Arms Collecting. These are unfortunately not available online, but you can get old-fashioned print copies from Joe Salter Antiques. I would recommend that you consider
Trade Guns of the Northwest Company, by Gordon T. Howard (
CJAC Vol. 2, #3, pp. 65-74) and
Trade Guns of the Hudson's Bay Company, by James Gooding
(CJAC Vol. 13, #3, pp. 75-91). Those two probably have the most information about Northwest guns, but you might augment your collection with Russel Bouchard's
The Trade Gun in New France, 1690-1760 (
CJAC Vol.15, #1, pp. 3-12) and James D. Forman's
Guns of the American Indians (
CJAC Vol. 11, #4, pp. 105-116). I think Joe Salter Antiques has probably acquired all remaining stocks of the
CJAC, and most issues sell for $5.00 each. Here is a link:
Canadian Journal of Arms Collecting
There are plenty of other references out there, but these ought to get you started. The links to the American Society of Arms Collectors journals online will take you to articles you can start reading immediately. I think you're on the right track, researching the guns that interest you. You will be a better informed customer when you order parts, a kit, or a finished gun. I believe you will be happiest with it if you have a gun that is as authentic as possible.
Good luck to you!
Notchy Bob