Hey Zandrew,I'm an optimist, but I think you should stick with your 50 shot at 850 fps with 15.99 JSB's, definitely with CPUM.I haven't done this tune yet , but I can get 62 shots at 850 fps with 15.99 JSB's out of my BAM B51 - 195cc air cylinder. The AT44 short has a 185cc cylinder.Things you must do:1) Plug 5 of 6 valve holes, lining up the sixth one perfectly with the transfer port.2) Narrow valve stem within the throat area.3) Open up the valve port and barrel ports to 11/64", vary your transfer port at 5/32" and 11/64".4) You should get 850 fps with a regulator set-point of about 1400 to 1500 psi. Test, you may need to tweak if necessary.5) Make the hammer pre-load adjustable using an external 4mm Allen Wrench. You'll need to set the pre-load tension so you're on the knee of the velocity curve.6) Test ................7) You may have to lighten the hammer by drilling holes if your not at your goal in 6). This is a lot of work, but can be fun Just depends on how badly you want you 50 shot count. Remember too, Bob has a very good point. Assumptions:1) Regulator & Plenum take up 35cc's or less (can't remember how much space they take). You can get away with a 18 to 20cc plenum; were only talking a 25.7 FPE shot.2) Regulator set-point = 1400 psi3) FPE/cuin per shot > 1.26% ( I think this is doable).Good luck .............. Kirk