Hey Gus,
I have been shooting a Navy Arms Charleville for a couple of years now. Love it! Just some thoughts;
"Here are some basic tips, find out the inside diameter of the bore. I use dial calipers for this."
In my opinion, an absolute must. When I first started out with it, I bought a pais of scissors moulds for it. It made balls that were actually .69 cal and would not fit down the barrel. When I finally did caliper the bore, it was somewhat smaller than .69 (.650 I think). I have tried various patch/ball combo's. {By the way, Track of the Wolf offers a wide variety of ball sizes.) Finally hit on a .648 ball with a .010 patch. Could probably go thicker on the patch but this combo seems to work good as far as ease of loading and accuracy. All this on top of 90 grains of FFFg Goex. One other thing I did was to put some thin weather stripping down the barrel channel of the stock. This gave a tighter stock to barrel fit. Enjoy your Charleville, once you figure what works best, they are wonderfull shooters. Would take one over a Bess any day!