My .22 D34 is shooting 14.5 super domes at around 700 fps. Given time and a tin or so, I wouldnt be surprised of your B25 increases to the same range. The jsb's are 16 gr so it will slow the rifle down more than the Crosmans. Mike is a stand up guy in my book. The entire planet would benefit a lot having more folks like Mike in it.
Theoben H.E. Gas Rams,..Shock the system!!!