The reason that the groups were poor for the pellets is that that rifle is turned up way too fast for them. Well up into the trans-sonic region above 1,000 fps.
The next evolution in AEAC Vlog should be to delve into whatever velocity tuning is possible on each airgun. If you would turn the velocity of pellets out of the NeutronStar down into the mid 800's, it would group them much better than the 1,000's fps you were trying them at. See Matt Dubber's excellent 10 part series on "Airgun Ballistics 101".
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https://www.youtube.com/watch?v=G1z4auc9hmE&list=PLJtIBVn6GmaTSkPSH96Vy7HWEdWO9iexY