Hammer Spring fatigue?
When gun came back from TT 4 years ago a 2700 psi fill would spit a 22 Kodiak from a 18″ barrel at 920 fps. Now a 2700 fill will start shooting in the low 400s and slowly increase to 700 then jump to 875 in one step. Checked tank pressure to be at 2200.
Striped, cleaned, changed breech O-rings. Everything looks good, found very little residue. PW set to max and TH at .055″ Moved TH to .065″, velocity dropped
It’s obvious valve is not opening fully till tank pressure drops. Can’t think of anything other then Hammer Spring. Thoughts?
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That is valve-lock. If Tony specified 2700psi and it used to work then its quite possible you are overfilling by a little bit, possibly your fill gauge is not right anymore.
Try a 2600psi fill and see what happens.
You wouldn’t think a valve would get tighter after 4 years, but you never know.
Your spring could have taken a set if you left it cocked for a while, but thats less likely IMO than your gauge being wrong. If the gun NEVER comes back to the velocity you had, then its the spring or the hammer isnt sliding as easy. (Polish out the frame inside).
get a new spring and find out?
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Well after Rachel shipped ALL the parts I ordered, I started with the hammer spring. Sure enough, that was it. With a 2750 psi fill it started at 850 fps, peaked at 916 then started to fall.
I don’t leave the gun cocked. If I take a pass on a shot I de-cock it till next time. BUT, I was storing it with the power wheel set at max which does load the spring. Now when storing, I turn it back to zero.
If that had not worked the brass insert without the O-ring mod would be the next thing to try. The O-ring does offer some resistance to valve stem travel. How much is enough to effect it? Don’t know. FYI when you order a brass insert from Air Force it now comes with the O-ring upgrade. Also the newer valve stems appear to be made from a stronger metal.