Yes, I got it working somehow now, but I still got problem: Gun works fine with Co2 but if I try to use HPA it fires like 100 times in a row. Any ideas why it does so? Too low pressure? How Do i adjust it?
there is a difference between HPA and CO2. Are you sure you don't have a low pressure HPA tank? F4's don't like to run below 500psi or so. They are designed for CO2 so you won't hurt the marker if you stay with it. Your velocity adjustment has to do with the recock as well as velocity. If you pull the cocking lever back it will stop the 'farting' so you don't waste air. If you are using a high pressure (800 - 850psi) HPA tank you will be better off...though you might still have to mess with your ram spring if you can't get it to recock properly. Did you have a ball in it at the time? That also makes a difference. The ball helps give backpressure to recock the hammer.
Polyurethane o-rings have a higher durometer (hardness) and will last longer. The black nitrile o-rings will not live very long.
No paintball in the desert. :-(