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Tuning Power Pup .25 Erratic Velocity

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Deeder

Deeder

Member
Dec 17, 2020
39
10
Texas, United States
My PP just got back from FX in which they performed a full tear down inspection and reseal due to it exhibiting significant velocity loss. When I first got the gun I tuned it to shoot 33.95gr at 930 fps and all the sudden it dropped to 740ish and nothing was changed on the tune. FX advised they couldn’t find anything really wrong with it just needed tuning. Upon return with FX tune, it was shooting the 33.95’s at 880…. So I turned up the reg to 130 and screwed in the power adjuster screw. Boom 964 fps so I backed out the hammer screw and dialed it in at 935 fps. After shooting 10 mags the poi is all over the place now. So I put it through the chrony, it’s all over the place on velocity 840, 888, 909, 921, 866 what in the Sam Hill is the deal?. Any feedback is much appreciated but I’m pulling my hair out. Thanks AGN
 
It would have been interesting to see what happened if you left the gun alone with the FX 880fps tune. You seem to be enamored with 930fps and turning the reg up and that shouldn’t be a problem if you work your way up to it properly. These questions are very difficult to answer when you don’t know anything about the guy asking the questions methods. Those are big swings in velocity so something is up. Hopefully you recorded the settings that FX set the gun to when they returned it to you. I would return to those settings and see if the gun goes nuts. It would be nice to know if their baseline tune went off the tracks also. Whether it does or doesn’t will still tell us some things.
 
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I worked up to the 130 ish bar setting (guages aren’t real accurate on the dreamline) and watched the velocity go up then turned down the hammer spring to dial into the 930’s just didn’t type all that out. I did not crank out the reg screw 3 full turns and go shooting 🙄. The gun shot very accurately at 935’s before and that is where I became enamored with that velocity. I did try to return the gun back to shoot 880 and it would never settle in and is all over the board. This model is advertised at 84 ft lbs my expectations aren’t too high. I have 3 impacts which I’ve tuned to shoot slugs 7-10 fps ES. I expect this model to sling 34 gr KOs 1050 fps based on achieving the advertised energy if I want to. At this point I cannot get it to hold a tune whatsoever. I shot 10 mags before it went off the tracks so based on that it could be expected the same would have happened with the conservative tune from FX. 
 
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Then it’s time to take the gun apart and inspect the hammer. Your gun doesn’t have a complicated valve system like your Impacts so we can rule that out. So unless your reg is binding at deferent settings, one of the only things left is something is going on with the hammer strike. Even if you overdrive the valve you don’t get the kind of swings you’re getting. Something could be going on between your hammer and sear.
 
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Disassembled and inspected the hammer, weight, and hammer spring and it all looks perfectly normal. There's no witness marks at least on the hammer where one could determine it dragging on the sear and everything moves freely in the bore. Spring isn't out of shape or bound up either. The reg doesn't bounce around on pressure I'll shoot and check it, it stays constant, it's not going up and down after each each shot. I also made sure the hammer adjuster screw maintains tension so as to make sure it wasn't changing position during cocking. It feels like my impact hammer adjuster screws which have "some thread compound" on them so they stay put. Also, inspected the barrel extension o rings in and out, they look intact. Which they should since FX just replaced them. Going to finish my coffee and do some more monkeying with the settings this morning and see what it does...... 

Please keep the feedback coming Vetmx I appreciate the thought process your putting into this for me!!
 
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Well it’s going back to FX!! Something just went “POP” and it dumped all the air out of the barrel. Something is broken and caused an o ring to rupture or valve to hang open. I’m not sure, but something is definitely wrong with this particular gun. 


Is there anyone with a Power Pup that can give feedback on their tune and performance?

Thanks again Vetmx! But I’m gonna hang it up and shoot my impacts now. 
 
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I have exact same gun same caliber. Put huma air high flow transfer port and pin probe in. Very strange things going on. Maxing out at 1010 with 25.39 jsbs. Got the hybrids going 965. Strangest thing is that the speed starts to fall off past 100 bar reg pressure. 95bar reg pressure with max hammer has been the best for me. Not having bad ES problems the hybrids stay within 960-970 and when I back back off the hammer spring the 25.39s stay around 865-880. Really wanted to shoot heavier slugs and this just isn’t cutting it. Should be able to shoot 38.5 Nielsen’s upwards of 960 FPS and still have a few Ft/lbs to go. Someone please help me reach this guns potential. Maybe heavier hammer and heavier spring?
 
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FX advertises 84ft lbs in .25… not even close.

Got it back from fx several weeks ago but it’s stayed in the case due to other activities. But they claim it’s tuned 945 with 33.95 gr pellets. Still not 84….. but I’d be happy with that!

Probably won’t invest any more into this platform though. My impacts are very satisfying to shoot and respond to every adjustment as intended.
 
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