The only Charleville I am aware of is the Model of 1777. I was not aware the earlier French guns were made at Charleville as well, but rather at Saint Etienne & perhaps a few at Tulle.
They are .69's and same calibre and models as used in the States.
The Charleville of 1777 had a very short 'pull' with a high comb, which was a cheek smasher.
The US issue paper ctg., up until about 1820, that is, held 165gr. of powder and a .64" ball. This charge included the 4 or 5 gr. used for prime.
It will be interesting to see this Japanese gun, as the brass pan of the Charleville was only used from 1777 on.
In around 1820, the ball size was increased to .65" and powder charge reduced in the ctg. to 135gr. which included the prime.
You may find shooting 70 to 90gr. is all you'll like.
As to reliability, well, that depends on how well made this gun is. The originals of 1680 through 1820 were just fine as the locks possessed much more sparking ability than needed.