That's REAL neat! Looks like you can do simple barrel swaps and caliber changes and just the probe if going 177. Is there a difference in accuracy when shooting AA variant of the 18gr JSBs?
If you are shooting only 25 yards out of a 22 caliber match grade barrel (dont laugh now) I would try the Crosman POINTED 14.3gr in the 175 count tins. I have many old Daystates, Theobens and old FXs that literally "stack them" at 25 yards (just like the good old unobtainable 22 Brown Box Premiers).