PT Extreme - too low velocity - please share debug hints

[Hooptie]

Greetings, my PT extreme velocity is very low, like 10feet range. But the semi action cycles just fine. The original springs look like a mix of Spyder on the hammer side and Nelson-based on the valve side. So I went with a Red main hammer spring and lighted valve spring that I could find. And still the velocity is too low.

I’m thinking there is some flow obstruction going on (and it just came to kind the bolt might be flipped). Anyway if anyone has experience, please share some hints to debug.

[flyweightnate]

Check under that cover on the left side. See if the gasket is going out, or if there's crud in there.

[zenmic]

Check the cup-seal. I have seen and have clean crud in there, not to mention the hammer is not very forgiving. The springs and cup-seal are are spyder and spyder clone parts. I should break mine out and see if it still shoots.

[GanonsGrin]

It also doesn’t help that the barrel bore on these is gigantic. Aside from that, the side port is probably the next thing I would check. If it were the cup seal you would likely have a full blown leak. As to the bolt, I feel like they were one solid piece and can’t be flipped over unless I’m remembering the bottom lug differently. Could there be a co2 filter hiding behind the valve that’s blocking it out?

[Trbo323]

Air passage or upside down bolt are the most likely causes

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[Chaos]

These aren't known for great velocity these days due to the huge bore of the barrel.... If you can get a tighter bore barrel made for it that will solve a lot of it....they are Spyder threads but the threads are in the wrong spot for just any barrel, probably a tight bore brass tube with a threaded collar would be your best option

[flyweightnate]

Checking your detent might at least keep the ball in the right spot, too.

[Chappy]

Youre running hpa I assume. Co2 will likely get you better velocity. Probably not optimal but will likely help

[Cunha]

These were never known for working well either, so you’ve got that to deal with too.

everyone else has good tips

[Trbo323]

10fps isn't just low velocity though. It wouldn't make much sense if it recocks but it's sitting at 10 for it to just be low velocity caused by something like the barrel or a bad spring. I would expect it to also not be able to recock if it were something like the spring, and maybe 10fps if it had no barrel at all but even a huge barrel should be able to give you more then 10

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[Toestr]

Yeah definitely something whack going on. Dry firing a blowback with no air and a heavy spring can send a ball like 10 feet.

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[flyweightnate]

Pull the internals and lay them out... I wonder what the bolt looks like

[Hooptie]

Hi, thanks for the all input.

Here are some more observations…

The barrel bore measures about .689 using Harbor Freight calipers. The bolt has no orings and orientation can only go one way.

The valve locking screw looks deep, not sure if this restricts the valve stem. The valve stem has flats, does this need to line up to clear the locking screw?

I changed my work mat from HK army to DYE, and used the new Dynasty paintballs. I can now get about 20 feet range. So a bit of improvement.

Another observation is the tank pressure is 790psi but the cheap ANSGear gauge on the dummy 12-gram shows 600psi. I think I’ll go after the hose line next.

[zenmic]

That is surprisingly clean for such and old gun. I might not be seeing something, but under the side plate should be a little rubber piece that is the ball detent. It should help with roll-outs, but considering the huge bore diameter for the barrel, roll-outs are going to happen. I remembered the main-spring guide rod being a little longer and made out of plastic. Is the one in the picture made out of metal?

I never had a "dummy" 12-gram with a gauge. I just used a spent 12gram to block that side of the valve. I ran a 4oz CO2 bottle, however, a 9oz CO2 give you a much better forearm rest. I understand that CO2 usually has an output in the 800~900psi range, so you might want to have your HPA tank kick up to be closer to the "high-pressure" output of high-pressure. I would oil, or grease all the O-rings.

Get a Spyder or more specifically a Rebel 32 spring kit. They should be relatively cheap and should help.

[GanonsGrin]

#13.1
GanonsGrin commented
Today, 10:58 AM
I don’t recall these even having a detent. Future proofing this design was something that I don’t recall being necessary at the time, I think it was just assumed that everyone had big enough balls to seal it up. I’m pretty sure that the bolt snugs up directly to the back of the barrel and that’s about it, there’s not a lot of real estate in these.

As another option, maybe try shooting it with a ball loaded in the barrel and shoot it straight up? That way the ball seats itself directly into the cup of the bolt and provides you the most pressure to get the ball out the barrel. If that works, then I’d say your most likely culprit is that huge friggin barrel bore. Otherwise, check to make sure your valve is clean. Aside from tank pressure and the bore, if it’s not leaking then there’s not a whole lot else that can be going on.

[Trbo323]

Push on the valve by hand, any restrictions beyond the valve spring? Install the valve with valve retention screw and use something like a screwdriver to push on the valve again, see if there is more restriction with the valve screw in

Heck you can take the valve spring out and see if there are any restrictions that way.

Do you have any 12g to try it with?

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