When I built mine, I was lucky enough to be able to ask Alex Efremenko, the recognized guru of French guns (by other gun builders of note) many questions and even sent him build pictures. His #1 advice?
"It must be trim with NO EXTRA wood on it. Remove wood. Do it again. Again ... and then when you finally have removed enough to where you think you ruined it ... you're done!"
Lock Area - Start at lock panels, ensure to add the finial on the end. Shape around under the lock too as there should be a slight depth transition from the lock area to forward where the forend starts. Sometimes that view of the lock area is akin to a snake head, i.e., wider than deep. Then work forward or backward.
Lower forend - This can be tough if your barrel breech area, where octagonal, is not tapered. (Mine wasn't - see photos to follow).
Wrist - Very small around, I go until I can touch my thumb to my fore finger, maybe even smaller (depends).
Buttstock - Carry the ballister line from the wrist way down. Look up some of Alex's guns, online or Facebook.
Upper Forend - A continuous taper to the muzzle, following the barrel taper. Look down from above and there should be < 1/8" to much less wood appearing outside of the barrel on either side. The web between barrel inlet and ramrod channel should be thin, danger thin haha! To make my forend appear thinner I scraped the ramrod hole or groove deeper and cut down the side height to show more ramrod, at least 2/3rds. Trim upper forend top to show 1/2 the barrel.
Be aware this forend will be VERY fragile without the stock in it. I found a wood dowel that somewhat matched the barrel diameter that I placed into the upper forend with elastics, if I had to do any work on it.
Ramrod - Must be very bulbous at the muzzle! I started with a 5/8" hickory bank (from Dan Putz) and turned it down to a 3/8" rod after a few inches, then fully tapered it all the way to and in through the entry thimble/pipe.
Front sight - A good ~5" back from the muzzle and NOT a turtle-shaped blade! They would be shaped like a barleycorn, made of brass, without ONE straight feature on it anywhere ...
Note that this one below, my 1st build, is in no way and NOT intended to be the
end all/be all of French arms, but even Dave Person on here commented on it, stating:
"Nice job!! Looks very credible as an early French gun." You can find that post under the title by me of, 'Tulle Fusil de chasse, albeit Left-Handed'.
Maybe these will help you visualize your's! Keep asking questions, that's how you learn! Also follow 'Rob M.''s post, as he's building one now. As I probably
missed a few other points, like filing in the barrel facets cut on the octagonal before the wedding band transition.