I checked the chamber and it appears to be 3-1/2". A new 3-1/2" 10 gauge brass shell fits with no play, as does a 3-1/2" new primed Cheddite. My Brownell's 10 bore chamber gauge only goes in to the 2-7/8" mark, but I have run into this before.
The entire twist forward section is exactly 1.00" outside. That makes the wall thickness from the butt section forward right at 0.10". The muzzle measures approximately 0.723". That amounts to a whopping choke of around 0.075" constriction.
I tried a tracing of the mark with no luck. I held it under a lighted desk magnifier and sketched it as well as I could. The picture is included. The arrow indicates the direction that indicates what I beliefe to be up. All the inspector and proof marks around it are oriented this way. Note that the box I sketched is actually the base of a square punch which was struck hard enough to impact the base into the barrel. The actual mark is only the curves inside. The mark itself is only about 1/4"square.
I had looked before at the littlegun.be link you listed. My gun is very similar to the first gun (the Model 16). However mine is much larger and, I believe built to a higher grade. The actions are very similar as to style and shape, but mine is built with a swivel underlever and wedge fore end attachment. The action has engraving and the wood is of a very high grade. Also, the guns shown are in the 15K to 20K serial number range. Mine is 44xx. The writeup shows they had shops in London and Liege. Mine is marked Galand Paris and is stamped as Manufacturer in Paris (in French). I have no doubt however that it was made and proofed in Liege and likely finished in Paris for that market.
|