I initially sighted in my STANDING rear sight for 100yd. zero, then the first flip-up leaf for 150 yards, then the next leaf for 200 yards. My 3rd leaf was then sighted for 300yards as we had a gong at that range.
Now I had previously worked up to my most accurate load which happened to be 165gr. GOEX 2F, a .030 12oz. Denim patch and a .682" pure lead ball. After sighting this in I happily found that a light plinking load of 3drams hit spot-on at 25 and 50yards with the heavy hunting load's 100yard standing sight. The first flip-up leaf gave me a zero at 100yd with that light load.
Note- my front sight was a Purdey designed bead barely higher than the top flat of the barrel.