As is not unusual with these Crosman projects, this one has 'evolved' several times over the course of several years. The latest evolution is swapping to "The Exclusive" side-lever repeating breech from China (via Ebay), and an aftermarket stainless steel bull barrel machined for a P-Rod, slightly modified for the side-lever breech.
Much preliminary testing involved trying to eke out as many usable shots as possible from the HiPac HPA conversion gizmo; that being only 9-10 shots with an extreme spread of about 40 FPS from a 1750 PSI fill. Accuracy was not impressive; come to find out completely due to the wide ES.
Once I knocked the fill pressure back to 1600 PSI a five-shot string looked like this- Low= 515, Hi= 523, ES= 8, SD= 4, Average= 518 FPS/9.5 foot pounds. VIOLA!!!
Now she averages .62" c-t-c five-shot groups at 25 yards, 1.34" c-t-c at 50 yards.
So now I'm considering a custom (length) chamber-tube, in order to return many more shots per charge.
One thing about evolution...
IT NEVER ENDS! $$$!!!