If it fires a few times, then all of a sudden doesn't cycle the bolt all the way... then it's gonna be drag on the bolt (if you've already changed the battery, dwell, etc). The plunger o-rings and the bolt o-ring are the likely culprits.
A way to test if this is the true issue is to turn up the pressure to 140-ish, and see if it fires. If it does, then turn it back down to 110-120psi and see if it still shoots. If it suddenly stops shooting... then bolt drag/friction is the problem. Hand-fit smaller/smoother o-rings.
Do not go gentle into that good night.
Rage, rage against the dying of the light.
Last edited by the other one : 05-12-2014 at 12:20 PM.