Just an observation, but the pellet strikes appear predominantly "doubles". Is this an artefact due to the substance of the backstop or are the pellet marks actually two adjacent pellet strikes?
On the basis of your remark that the wads feel to be a slack fit in the hull, can there be gas leakage to account for the pattern irregularity and distribution of pellet strike?
I think the double marks are a Sharpie pen next to each pellet strike indicating it has been counted. I noticed the same thing and wondered for a moment how that could be.
I do think that loose wads will have an effect on pattern (and efficiency of the load in general. In fact, I know it will.
