I wonder if it was full charge FFg or if it was a light noise and smoke load.
most of those era muskets would only take around 70 grains of FFg ..quite different from todays inline magnum loads with 150 or more grains
* can also use FFFg in a 45....judgment call
Almost all of the re-enactors use replica muzzle loaders -- any surviving original is way too rare and expensive to carry around in the field.
The replicas are built with modern steel and can take what would be substantial overloads for the originals.
I have seen a 150 lb feral hog hit with a .58 cal ball, which penetrated completely through the lungs and ended up just under the skin on the side opposite the entrance wound. The ball had expanded to a flat piece of lead just about the size of a US Quarter.
* can also use FFFg in a 45....judgment call
You can stick 90 grains FFF in them no problem. Only if the barrel is old, pitted and generally not taken good care of would you want to cut that down a bit. Or a 50 cal. 90gr is a little uncomfortable for a 50 cal flintlock style musket. I have a 50 carbine percussion cap that I have no problem stuffing 110 grains of FFF in, launching a 180 grain hornady 45 cal boattail/sabot. knocks deer right off their feet at 200 yards, 4 inches drop.