Daystate air ranger fps variation

[dair]

As others stated change the bolt O-ring as that is part of the problem. I too have an FAC .22 cal Ranger and experienced inconsistent velocity variations and poor shot count when using lightweight pellets. I noticed that when I switched to the really heavy pellets like Eun Jins combined with a high fill pressure the rifle seemed to really settle down. I also spoke to Gary Sanders a few years ago and he confirmed the FAC rifles were tuned towards the really heavy pellets combined with a very high fill pressure just as I found out. I think you will see a big difference in energy too when using the heavies as well as a much flatter power curve and increased shot count. Your sweet spot will probably be at a much higher level and require refills a lot sooner than most rifles. It would be interesting to see if your rifle responds as well as mine did to the change. Mine is an earlier 50 ft lb version so that might make a difference compared to later models as they might have made changes to the valving.