Today I ran a pattern test to see if loading a plastic shot cup would give tighter patterns from my Navy Arms double barrel shotgun. All the patterns were fired off-hand from a marked 30 yards. I only shot the left barrel (marked modified). I was expecting the shot cups to give something close to a full choke pattern. I loaded the gun with my best load. 80 grains of Goex 2-fg powder and 1 1/8 ounce of #8 shot. The only variable I changed was the wads, cards, and shot cups.
This first pattern was shot with my normal loading in order to set the standard.
Powder, nitro card, 1/2 cushion wad, over shot card, shot, over shot card.
This load used a brown CVA shot cup which was sold for muzzle loading shotguns. As you can see, it produced a doughnut hole pattern. The shot cup left it's mark to the left of the center. Not a desirable pattern at all.
Powder, nitro card, CVA shot cup, shot, over shot card.
The third pattern is a very evenly distributed pattern but much wider than a modified choke should produce.
Powder, nitro card, Winchester WAA12R wad, shot, over shot card.
This pattern is wide and sparse. The WAA12R wad was loaded directly on the powder.
Powder, Winchester WAA12R shot cup, shot, over shot card.
Pattern five is the best pattern I got using a shot cup. I cut away the bottom part of the wad, loading only the cup on top of a nitro card and 1/2 of a cushion wad. However, it is a more open pattern than my standard load.
Powder, nitro card, 1/2 lubed wad, Winchester WAA12R with bottom cushion part cut off, shot, over shot card.
Pattern six Is the CVA shot cup loaded with a nitro card and cushion wad between it and the powder.
Powder, nitro card, 1/2 cushion wad, CVA shot cup, shot, over shot card.
Another pattern from my standard load with no plastic shot cup.
It remains the best load from my shotgun.
Powder, nitro card, 1/2 cushion wad, over shot card, shot, over shot card.
My conclusion:
The Winchester WAA12R wad with the bottom cushion part cut off loaded on top of a nitro card and 1/2 of a cushion wad gave the best pattern of all the shot cup loads. But it is not better than my original loading without a shot cup. Therefore, in my shotgun I was unable to improve the patterns by using a plastic shot cup. I also noticed some plastic fouling when I cleaned the bore.
Based on today's test, plastic shot cups did not tighten or improve my patterns in any way.