I stock and use only 3F and 1-1/2F Swiss black powder.
3F for ALL flintlocks, in both tube and pan, whether .32 or up to .62 in bore size.
1-1/2F for the .45-70 PPB (paper patched bullet) cartridges for Sharps falling block and Remington rolling block rifles.
1-1/2F works just fine in any flintlock, too, and have used it with flinters of all bore sizes.
For the very most part, back in the 18th century, the most common gunpowder was grained to about 1F at best,but I'd say that coarser cannon grade was most prevalent. "Very fine" powder was at best 2F, and reasonably rare to find unless coarse powder was wetted and ground or screened finer.