ordered a pelletgage...got a .22 one on the way also, decided im going to size every single pellet i shoot now to make sure i shoot what i know will work.
I just read Tom Gaylords part 4 review of the pelletgage, interesting results with boxed prems.
Remember the pellet is a valve, depending on barrel fit will alter the release pressure, larger headsize will induce increased friction...air density and moisture content also have a big part to play.
last...get off JSB's, try something else, just for sh1ts and giggles and see if the gun does the same thing, regardless of velocity you just need accuracy and test. It would be seriously interesting to here if the POI shift vanishes once the pellets are changed as right now i bet 99% of those with the issue keep using the same pellets throughout the testing they do.