The French Army Museum at the Invalides is a place where you definitely would like to go.
BP Hughes has three excellent books on artillery which I would highly recommend. Roundshot and Rammers by Harold Peterson is another good title. You might also want to try Google Books and put in key words such as 'Gribeauval' or 'Gribeauval System' and go from there.
You can also try the Smoothbore Ordnance Journal on this site. There is quite a bit of primary material there.
You can also go to George Nafziger's site and there is an English translation of Jean du Teil's Usage, which was the only doctrinal publication of the period that addressed artillery issues above the battery/company level.