I've found the same. My last batch of JSB were great, this batch are pant's in comparison. I've posted a thread on here recently about it and cleaning my barrel.
I've just ordered 4.51, 4.53s (a tin of each) from intershoot to try out some more tests.
Sometimes I think we're all to anal, but these pellets (even at my level) make it a bit of a lottery.