I bought a pelletgage from the US as I was having severe issues with a batch of JSB exacts, muzzle velocity was anywhere from 670 to 780fps with the pellets right from the tin, however I bought a second sleeve with different die and manufacture date (still 2015) and sorted them for head size. I bought 4.52's
getting less than 100 4.52's from 2 tins shocked me somewhat, however plenty of 4.51 and 4.50's with a few 4.49's that shoot rubbish.
So then i moved to test a few in my TX, this has 1 22mm piston and since the conversion is very JSB batch and die specific. I chucked in some 2013 made exacts also....40FPS difference quite shocked at this.
I actually did sample a few shots from the earlier 2015 batch....they are utterly shocking, however they shoot just fine thru my LGU which does have a much tighter barrel than the TX does.
So...take from that what you want, I know the 2013 batch of exacts i have shoot superb thru the TX, power is slightly lower than with the superfield 4.51 but accuracy is as good if not better. The newer 2015 head size sorted batch the velocity is just shocking...how can i go from a batch made in 2013 to a batch made in 2015 and lose 40fps?
All Exacts under test were purchased at 4.52mm, none have been weighed however yet, the test was head size only.
My next task is new barrel for the TX, the LGU out shoots is with pellets it just can not handle.