My flintlock has a low sweet spot at 62gr and high sits at 83gr. That's for a .490 ball and .015 patch.
If I shoot a .495 ball with a .010 patch, the low increases to 65gr and the high goes up to 85gr. Not sure why, just what I've observed over the years.
About 90% of my shooting is with the .490 balls and 62gr at the range, 83gr under the same ball when after deer. One of these trips I'll remember to shoot up the remaining .495 balls just to be rid of them... The .490 balls seem to be vastly more common/available.