Alright, I did a whole bunch more shooting today and basically ended up back where I started.
I described the gun in my previous post, but for those who didn't see that - it is a 12 gauge double flintlock choked mod. and full. I've moved from #6 shot to #4 shot and I am shooting some pretty stout loads due to the fact that I was not getting the knock down results I wanted while duck hunting the last couple of years.
Today I tried lots of different combos - with plastic cups, without plastic cups, 1/4 inch wads, 1/2 inch wads, wads above shot and wads below shot, more shot, less shot, less powder, etc. I shot at a 36" X 36" piece of paper to see the size and quality of the patterns. All shot from 30 yards.
These barrels don't like the thick (1/2") wads anywhere in the loading process. They totally destroyed the patterns when placed below the shot, and added some big holes in the pattern when placed above.
The loads with 1/4" wads seemed to behave the similar to the 1/2" wads but without causing quite as much damage to the pattern
The best patterns were this:
100 grains of FF, two overshot cards, one slit plastic cup, 110 grains (volume) of #4 ITX original, and two overshot cards on top of everything. This loading gives decent patterns without too many big holes in the pattern. This also give me plenty of velocity when put to the "tin can" test.
So, since that is the loading I've been using the last few weeks, I know where the problem lies - with ME! :surrender: The ducks that I knew I'd made a good shot on dropped like stones, but the ones that got away clearly can't be blamed on poor patterns.
I think Skychief is right that with choked guns his system may not work as well. But I find it very interesting that any wads below the shot gave the worst patterns out of this gun, no matter how I loaded it.