Holes in the pattern are a big issue with muzzle loaders.
I am not talking about variations in the pattern that you can place a clay bird in, but rather a circle 6" in diameter with no holes, shot after shot.
There are so many causes and cures it is difficult to say why it happens. I have closed the hole by adding an over shot wad under the powder wad, changing the power and/or cushion wad thickness and by simply cleaning the fowling after a long day of shooting.
I have not patterned my breach loaders after a round of black powder skeet but I bet it would be interesting. I can not say I have had any difficulties with low pressure smokeless and shot cup wads.
