PMI Piranha not cycling properly - ideas?

[Drcemento]

Re-building for one of my sons friends - top to bottom tear down, Piranha STS all new o-rings, properly re-assembled. airs up fine. cock the bolt pull trigger and get massive fart/machine gun for a second but does not re-cock. 820psi from the tank. Does have a red main spring.

[iamthelazerviking]

Have any CO2 to test with?

[Trbo323]

Shove a barrel swab down the barrel. Piranhas don't like to dry fire without a little back pressure. They were designed around CO2 and the slight difference in energy density makes the difference.

The piranhas hammers are larger, more mass needs a little help. I've always wondered if you drilled a few holes how that would effect things

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[Drcemento]

wow thanks Trbo323 - put some paint in it and it fired just fine. now for problem number 2 - cant get more than about 240 - super small graffiti, adjusting velocity adjhuster makes 0 difference from halfway in to full in. any tricks to bumping that up with HPA? I do have Co2 and will try that for fun but may not be practical

[Drcemento]

thats crazy - dry fired perfectly with Co2 and chrono's right at 280 with the adjuster most of the way out. kids lucky - I can fill a couple tanks for him on game day. would still like to try and get it rolling on HPA for fun.

[Trbo323]

Pull the back block out and make sure the adjuster is actually able to move the spring. Sometimes they had a little flat disk in there that the screw pushes on and that is what the spring also rests on. People who don't know what they are doing take it apart and lose the little disk then the screw doesn't actually adjust spring tension

If it is in there the easiest thing would be a longer barrel

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[PumpMan10988]

I gained about 20 to 30 FPS just by properly bore matching with my spyder. I was also stuck in the 250s. A lighter valve spring is worth trying too.