Chrony help, velocity spike
What would cause a 50 fps spike in velocity during a flat string? I have the shorty shooting 18g @ 800 fps, like 2-3 sd, then every once in a while I’ll get a jump up to 850 fps just for one or two shots.
I pulled the reg and cleaned out the GOBS of silicone(?) from the factory, gave the washers a light coat of moly and silicone on all o-rings which looked to be in good shape. Also the set screw in the reg adjusting cap was loose causing the cap to turn slightly, tightened that up. All this seemed to help reduce the frequency of the spikes, but I’m still getting a few during a string.
What else can I check? Thanks.
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Dman, do you know what size that screw is? And thanks for the tip on the o-rings, I saw the o-ring thread and need to put in an order.
Also, how does the valve unscrew from the action? I undid the set screw on the bottom of the action, not sure if it did anything, but still could not get the valve to budge.
In this video around 3:00 he unscrews it easy as pie… https://youtu.be/rEc6X9x8LcQ?t=3m6s
I tried using a leather strap and channel locks, gave up because I didn’t want to break the damn thing…
Also pulled the reg again and cleaned just in case. Also noticed a lot of oil in the air tube, enough to puddle up. Cleaned it out. Opened a new tin of JSB 18’s and backed away a bit from the chrony. Now shooting consistent 790’s. I’ll check again in the morning.
I should of said this before… but next time you take your regulator out.
Change out the 2 Orings on the inside shaft to eurothane 70d …
Also get yourself a nylon tipped screw for the adjuster. That way it don’t bung up your threads and it keeps it locked down.
Thanks guys, I did just that.
Also pulled the reg again and cleaned just in case. Also noticed a lot of oil in the air tube, enough to puddle up. Cleaned it out. Opened a new tin of JSB 18’s and backed away a bit from the chrony. Now shooting consistent 790’s. I’ll check again in the morning.
Sounds like you got the 15.9s mixed in with the 18.1s
:rofl:
Sloth, Dman’s comment is very likely. IF you are shooting 18g at 800 fps, then 16g would be around 845 fps and 13.4g would be ~890-900 fps.
Get a new tin and redo the chrony to see if the spikes are still there.
Sounds like you got the 15.9s mixed in with the 18.1s
Inconsistent sized pellets will do it every time, I use my new old stock JSBs when I’m checking for fps consistency. I think Dman \/ below is correct but I think you may have some 14.3gr mixed in for a 50 fps difference.
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That set screw in the hole on the bottom of the action holds the Brass valve body in place. That is what the Valve sits againts.
Anyhow… To remove the Valve assembly ( the piece threaded into the AT/ and block)
Ideally find 2 drill bits that fit in the holes perfect ( not the cutting ends, The end that goes into the drill )
Tape up the cutting part of the bits so that you can use them as a lever….. put the action in a vise or something to hold it firm.. then stick the bits into the 2 holes and turn it off. Some times they can be tight as shit… but just make sure that the Bits fit tight and use both holes so you don’t elongate them,
Should be pretty easy..