After shooting my new to me flintlock, I've recovered many of the patches down range. What should these look like so I know that I'm getting the best performance possible? Or rather what shouldn't they look like?
Mine always look like they could be shot again. Look for holes in the fabric weave. Lube makes a big difference. I use Mink Oil from Track for hunting and Hoppe #9 patch/solvent at the range.
A small ball of wasps nest under the ball can protect it and seal the bore with thin patches.
Use the largest ball and thinnest patch that will hold together for best accuracy. By looking at the spent patch you can tell if gases are leaking by the grooves.