At a typical reenactment we have 4 battles, I bring out 16 charges each of 7 ounces for each one. (Note, not my gun - full size 3" Wrought Iron Rifle, but I do the care, feeding, and hauling of it so I get to be gun sergeant, with the owner being crew). Our first load is always a double, then mostly single charges. If we are tucked back, well away from the spectators we stick mostly to single charges. If we are where the public can really see and hear the gun, we will fire 3 or 4 double charges. Most battles I end up taking about 4 charges back to the magazine.
If we have a school day the day before the event, which is the case for 3 of them, we need another 14 or 15 charges. And of course the friction primers. It is tempting to go to quills to same some money.
So, minimum of 24 pounds of powder, and maybe about 60 primers.
That is better than the guy who bought a 12 pound Napoleon from Steen, 4.62 inch bore. Steen reccomends a minimum of 1 pound loads for it. I THINK it could go down to about 12 ounces. Less than that and the primer might not hit the charge.