My load for the old muzzleloader was developed over about a year of trial and error. When I started I was lucky to get one pellet in the brain and neck bone at twenty five yards. The gun is cylinder bore in both barrels as is the case of guns of that era, circa 1860. Some shooters have had their old guns jug choked to improve patterns There you must have enough wall thickness in the barrels and I was not willing to go that route. I decided to see if I could build a load that would have a dense enough pattern with good penetration to kill a gobbler at a maximum range of 25 yards or less. As of 2019, the six gobblers I have taken with the gun have been shot at ranges of between 11 and 20 yards.
Anyway, I started trying traditional loads of different combinations of grains of powder, 1/8″ card wads, cushion wads, equal volume of powder and over shot card. Nothing worked. I went and talked to many muzzle loading enthusiasts trying out their advice still no success. Then I saw that modern inline muzzle loaders were using plastic shot cups. Got some and cut them down, some improvement, still not there. Found Ballistics Products and ordered some of their wads. One that made an improvement in pattern was the unslit BP12. I custom cut it to hold 1 1/4″ oz of shot and cut four slits 5/8″ long in the sides. This cup also has raised ribs around the OD which decreases friction and amount of plastic left in barrels. Next improvement came after trying all types and sizes of shot the best patterns were with #7 Nickel plated shot. Nickel plated shot has a harder than lead, outer skin that is much smoother than lead. When a bird is hit with NP shot it does not draw feathers into the hole like lead resulting in better penetration. I cut over shot wads from egg crates with an old 12 ga choke tube. They fly away the instant they leave the barrel and do not disturb the shot pattern.
The final load which consistently puts six to seven pellets in the brain and neck bone and is 26″ across at 25 yards uses 1 1/4 oz of shot with equal volume of FFg black powder. I always fire a cap into each barrel to make sure the nipples are clear and dry out any residue that might be left from cleaning. Then load the powder, followed by 1/8″ card which acts as piston, then 1/2 lubricated cushion wad that also keeps the fire from melting the plastic cup, then the cup and 1 1/4oz NP #7 shot, last the over shot wad.
In addition I ordered a hone and worked it through both barrels. I did not see an increase in pattern efficiency but noticed that it made the job of loading and cleaning easier. I can clean my gun faster than I can clean an single barrel inline gun. One thing I had not counted on was the way the gun has become an extension of myself. The process of loading, firing and cleaning have taken on new meaning. No wonder the old timers gave their guns names!