I have a suggestion to improve your pattern density.
When I was patterning my 16 gauge trade gun I first use 75 grs 3FFF,3 overshot cards, felt wad, overshot card, 1 3/8 ozs copper plated #5,over shot card. My test target was at 20 yds. The image below was the results.
I then added Jiffy corn-meal muffin mix as a buffer for the second target. Since I didn't have any other turkey targets I use an 8" splatter target at 20 yds. Picture two shows the results.
Granted 20 yds is close but, I needed to start somewhere. What I need to do is continue to increase my range until the pattern is no longer acceptable. Unfortunitly work and family has taken a major amount of my time. I will post my newest results as time permits.
I used muffin mix not just straight corn meal; it has added fats that is not in plain corn meal. It has a stickier consistency. Not knowing how much to use I took clear plastic tube punched a hole in the bottom. I placed an overshot card in the bottom, added the shot, then started with the corn meal muffin mix. I added a little at a time and tap the sides of the container to get the mix to filter down. I used a LEE dipper don't remember the amount I'll check when I get home. I continued this until the mix surrounded the shot. It takes quite a while to get the muffin mix to filter down around the shot. I then placed another overshot card in the tube, placed it on top of the barrel and used a small dowel rod to get everthing in the barrel. With a range rod I seated the whole thing. I plan to use this same concept for loading in the field, it may not be PC but......
The gun shot a little left but that is easily fixed. I was just concerned with pattern density.