Jack,
If you can find a copy (copies) of Russel Bouchard's books, in English: "The Fusil de Tulle in New France 1691-1741" Historical Arms Series, Museum Restoration Service, c.1998, 48 pages, and/or in French: "Les fusils de Tulle en Nouville- France 1691-1741" Publication du Journal des Armes eng. Chicoutimi QC, c.1980, 109 pages, they would answer a lot of your questions. Note the two books are not identical. Am not sure if they are still in print, so may be hard to find. I did meet a guy who was building such a fusil. He had taken the modern castings for the hardware and ground out the back sides of them to make more realistic and that would result in making them lighter. Proper bore size was 28 ga. for 28 balls/Livre of lead, bore dia. tolerance .577-.623 in. They would aim for the smallest dia. and if there was imperfections, continue to bore it out until it cleaned up or they surpassed the larger tolerance (i.e. junk) Also T. M. Hamilton's book "Colonial Frontier Guns", The Fur Press, Chadron, Neb. c.1980, 176 pages, would also be useful.
I also recommend Alexander Efremenko as a good maker. He has a web site. Best of luck with your build. Please let us know how it progresses. Hope I got the right ill.?
Doc Shaffer