I'm curious, I have an Airforce airgun with both a 12" .22 and a 12" .25 barrel.Today I was gathering some data on shot strings and thought I would try the 25.39's in both calibers. First I shot the .25. It averaged 825 fps over 50 shots with a 3000 psi fill. Changed out the barrel to the .22 without changing any settings and it averaged 809 fps with fewer shots. As far as difference in shot count, that could easily be me not being careful when refilling the tank, but I would have supposed they would have been very similar speeds, or maybe the .22 would have been slightly faster. Is there a reason why a .25 would shoot faster than a .22 with the same weight pellet?