while similar, the 1795 springfield is not an exact copy of the Charleville. the bayonet lug is on the bottom of the barrel on the springfield and the top on the '66 Charleville. there are small differences in the barrel bands as well. there are likely other small differences that I am unaware of. be careful the stocks may be different. the '66 Charleville had a thin barrel, part of the pattern change from the '63 to lighten the '66, the springfield also had the thin barrel like the '66. the springfield stock may not be inletted enough if you have the thick barrel. There is no forearm on the Charleville pattern muskets, they all had one piece stocks. the forestock is generally the part of the stock in front of the lock. all Japanese locks I have seen use coil springs , or a combination of flat and coil, so lock inlet may be different. my Japanese flinter has coils and is smooth as butter, but the geometry is off a little and most sparks miss the pan, and the frizzen is not hard enough and has fewer sparks than I like, but it usually fires ( with a little lag). considering your stock was glued, you would be better off having it duplicated in a one piece format. My Ramrod has no spring it rubs against a pin through the stock and screws into a lug on the trigger guard. good luck repairing it, I hope it works out ok for you.
