Dennis
Someone with more knowledge of how the mid barrel tuner works will have to chime in. I honestly have no clue. Another member here told me where to locate it on the barrel and how to tune it. So I did as he said and produced the group pictured.
As for aim point per the other poster asking. There is a little tiny dot in the center of the target. I aimed at that and fired away once it was gone I just centered the dot of my scope inside the ring and just kept shooting.