FX Crown low fps

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Arvid

Arvid

Member
Jul 24, 2018
47
3
Trøndelag, Norway
Hi all.
Have just bought FX Crown .177. Having trouble getting desired fps. Have read a lot on this forum and have tested all the advice regarding adjusting the regulator, hammer jump and hammerspring screw. Max speed is as far as 750 fps with JSB 7.33 and 620 fps with JSB 10.34 gr. It's almost so I think that the rifle is adjusted for UK market? Does anyone know if this might be the case? Without adjustment, straight out of the box was max fps 520 with JSB 7.33 gr. Hard Air Magazine has tested the same rifle as I have and achieves 894 fps with H & N Baracuda Match 10.65 gr. Anyone who has experienced something similar? Highly appreciate feedback and suggestions.
 
Hi Arvid,



Where the magazine goes into the breach, there is a small hole that is drilled into the slanting part, inside this there is a shipping set screw that prevents the hammer fully striking the valve, sometimes dealers forget to remove this and the gun produces low power, check and see if its still in there...
Click to expand...


Thank you very much for the tip! Looked at this screw earlier, but found no info about it and could not find it on the split chart. The screw is there. I will remove the screw and test tomorrow. Late in the evening here in Norway now :)
 
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Hi, did you buy the gun from sweden? If that is the case they might shipped you the 10 joule version, because swedish law forbid shipping airguns abroad with higher power than 10 joule, directly to customers. If you bought it from a dealer in norway, and lives in norway, you should get the none restricted version of the crown. 

If it is a 10 joule version. There should be letters wich says "10 j" on top of the gun. The difference is that it has a weaker hammer spring, different valvepin spring, and the internal holes in the power wheel is smaller. If you have a 10 joule version, you can by a "power kit" from a dealer in sweden legally, wich contains the mentioned parts, making the gun none restricted. If you bought it from a dealer in norway, I would demand they send you a full power version, or atleast install the mentioned parts for free. 
 
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Hi. 

Thanks again for advices and all help ?. Riazp where spot on! ?

I found out that my FX Crown .177 did have the shipping set screw still in place. Its been taking a beating of the hammer...the treads are flat. Even so it was reasonable easy to get out. With everything adjusted back to "fabric settings" i got around 300 ms /984 fps with 8 gr pellet. So now the tuning starts. I usually shoot at 50-140 meters at various steel targets with my regulated AA S510 Extra FAC .177 using H&N Piledriver 21 gr. Would like to do the same with the Crown, but the H&N Piledriver 21 gr does not go well in the Smooth Twist X barrel (as predicted). And so far it does not group well at any distance between 40-70 meters with any of the JSB pellets (i have them all) ? At 20 meters its doing very well. Was hoping to do better at long range with JSB Exact Beast 16,20 gr but as of now they are all over the place. Guess i have to tune for more velocity. Also planning to upgrade the Crown to cal. .22 og .25. Not yet decided on witch cal. to choose. It will be used for target shooting only since its not allowed to hunt with airgun here in Norway. 

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1533218706_1314564925b630f92d88e47.04174651_IMG_5948.jpg

 
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Hi Arvid,



Please try JSB 10.34 at about 910 to 930 FPS, regulator at about 95 to 105 bar, you will need to adjust the power wheel and regulator so that you have not too much wasted air after the pellet, sorry I don't have measurements for power wheel distance as my crown is not in .177...



I am shooting .177 in an Impact, also using smooth twist on that gun not twist x, but am grouping between 1 and 2 inches at 100 yards, I was surprised how the faster speed affected accuracy with the 10.34 and smooth twist barrel, perhaps you will have luck with a similar configuration with your crown.

I live on the other side of the world but will be happy to swap your .177 twist x for my spare .25 twist x :)
 
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Glad to see you found the problem. I have a .177 wildcat mk2. It has the same x-liner as in your gun. I did not got my gun to shoot 8 grain jsb well until i tried a tin with 4.53 mm. My "old" tins with 4.52mm was probably undersized (smaller than 4.52), so they did not shoot good. I did pull several brands of pellets trough the liner when I had it of the gun. And could see with naked eye that the barrel had gripped better on all (stoeger x-field, RWS superdome, and 4.53mm exact) except the 4.52mm I had. Could see difference from the 4.52mm and 4.53mm. Also the other brand pellets wich gripped better in barrel did shoot better, until I tried 4.53mm exact. So if you want to try jsb exact again, you might try a tin with bigger head size to see if they shoot better. 
 
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I have a UK restricted crown. I have changed the 22 barrel for .25. And main spring for fac. Changed valve spring for fac international version Cranked up regulator to 150 bar. Tightened spring tensioning screw to full and have power wheel on max the front wheel that turns from 177. .22. .25. .30. Low. I have drilled out the hole on .25. I have drilled out the barrel hole to max but still I can only get 25 ft lb and 680 FPS. What else should I do? I need to get up to 900fps would a huma regulator get me there ? Do I drill out the regulator port to let more air through?? Anybody please help I am desperate. 
 
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