I was going to buy an in line muzzleloader, but my father just gave me an old cva kentucky flintlock in .45. I'm not planning on hunting with it this year, but I might take it for whitetail next year if I like it. With a patched ball, what's a good hunting load? What kind of range/tragectory can I expect? What kind of accuracy can I expect? There's no way I'll ever stop loving my breechloaders, but I think it'll be fun to shoot some deer with the same rifle my father used 25 years ago.

You can't eat what you miss!

Ask your father. If he killed deer with it, why ask anyone else??

Keep yore powder dry!!

I would suggest you start with 60 grains of black powder and work your way up from there. I would not exceed 90 grains, some of them older rifles were not designed for heavy loads.

80 grains is probably enough.