My .177 at44 hated JSB also but after i polished the lead and port in the barrel it shot them better and gives acceptable group size but still not as good as H&N baracuda head size 4.52. My thoughts on the problem with the JSB in this rifle is caused from rough spots that damage the softer JSB pellet. I could be wrong but seems like the JSB could be soft enough to still be getting caught on something during loading.
Best accuracy from a pellets happens at less than 950 fps MAX in my experience. I try to keep all my pellets at 925 or less. That may be why you aren't getting the best accuracy.
Those are nice 30 yard groups! Bet it makes it all worth it![/quoteIt does. Especially when you sit down & shoot paintballs out to 40yrds with a gun that used to shoot a 2 1/2" group at 30yrds.