Strange FX Impact problem

Forums PCP Airguns Strange FX Impact problem

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    Kallstrom
    Participant
    Member

    I’m having a strange problem with my .30 cal FX Impact. The adjustable air regulator is set to 150 bar, the power hammer spring adjustment is set to max, and the valve return spring adjuster is opened. With these settings I expected to reach 840-850 fps with a 50 grain pellet, but when I study the chrony the shotstring starts at around 650 fps. After 10 shots the velocity goes up to 730-740. After about 20 shots the velocity rises to 770 fps, and finally, after about 30 shots, the shotstring reaches a maximum velocity of about 810. I can’t feel or hear any obvious leaking, although the rifle losses pressure at a slow rate (maybe 20 bar a week). What could be wrong? I would be very grateful if someone could point me in the right direction.

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    Michael
    Keymaster
    Keymaster

    Sounds like a common string from an unregulated gun that was over pressurized.

    Try turning the valve adjuster down a bit. Make sure you can see the last line. It may be wide open & wasting air.

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    Michael
    Keymaster
    Keymaster

    Also, if you’re losing 20b a week then there is an o-ring somewhere that needs to be replaced.

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    BRS
    Participant
    Member

    Fist of all you are citing 2 problems here – and they are most probably unrelated.

    The first you mention has been covered by Michael above – it’s the standard ‘Bell Shaped’ power output curve (when depicted in a graph) shown by all unregulated airguns.Assuming a fill of 220 BAR – only the middle section, approx 180 down to 110, will provide consistent FPS- that’s a fact of Nature (immutable Physics).

    The weight of pellet used at your desired FPS seems near impossible and somewhat fantastical !  Why those choices? 
    Having everything adjustable set at ‘max level’ is not a good starting point, anyway.

    The second area of your concern is the 20 BAR air leak per week (with your rifle), most likely culprit is the air inlet valve ‘O’ ring – the tiniest speck of dirt is enough to cause trouble with these very small ‘O’ rings. Lots of discussions on here about these articles (that ‘O’ ring) and availability, have a look around.
     

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    carpp
    Participant
    Member

    i had this problem where it was set to max and i couldnt get over 820fps with a .25 33grain pellet where other people were getting 840-860, about 150 pellets later the gun broke it wouldnt let air through to the barrell, they wouldnt repair it on warranty and just replaced the entire action, with that action i could get over 820fps.  Not sure why it was they never said what was broken inside just that it was unrepairable.

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    Tominco
    Participant
    Member

    Michael and BRS have said the same stuff I would have so, no need to repeat it. 
    It sounds to me like you over adjusted your rifle. Bring it back a little and see how it turns out. 
    Here’s a link to my top speeds. I haven’t revisited those settings because I have no need for it and they are horrible for air consumption. 

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    Kallstrom
    Participant
    Member

    Thank you for your speedy replies. carpp: I hope my Impact won’t need a complete rebuild, but now I’m mentally prepared!  At first I used the Impact with a .22 barrel, and I didn’t try to max it out. I used a chrony at a friend’s house, tested a couple of shots and found a setting that produced a velocity of about 920 fps (13 grain pellet). In 22. cal with 13 grain pellets the rifle still produces a fairly consistent velocity around 920. The first time I realized that my Impact couldn’t reach the advertised powerlevels was when I bought a .30 barrel and borrowed a chrony. Even on max settings it isn’t close to the numbers that Tominco recorded (thank you for the link). When I reduce the valve return spring adjuster and the hammer spring the power drops even further (550-600 fps with a 50 grain pellet). Everything seems to work in .22, but something prevents the rifle from reaching higher power levels. I’m going to keep on plinking with the .22 barrel, but when the autumn comes I’m going to start looking for a repair shop.

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    Verve
    Participant
    Member

    Fps you are quoting are far too low. My Impact shoots 18gr .22 pellets at 960+ and 920fps on 25.4gr .25 at just past 2nd line on the valve.

    When you close the valve knob fully, which line does it stop to (don’t force close as there’s a rubber ball in the knob, just when it stops without applying lots of force)? Picture possible? On full close, it should be half way between 1st and 2nd line or close to 1st. If you can see the second line on full close, send it in for warranty repair.

    Either the transfer port is not aligned or the valve stem as come loose from one (or both) ends.

    Slow leak is another issue but it shouldn’t have any such major effects on the fps.

    Also, check for play in the power spring when set at Max power. Set the wheel at Max and check for play in the black metal plate to left of it. rifke shouldn’t be cocked for this check.

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    Txboy
    Participant
    Member

    Not sure how many shots you have through your rifle but after about 5000 the poly washer that hammer strikes ever time you shoot wares out. And gets pinched between the valve rod and the hammer and creates resistance and will not let the valve open properly. In turn your fps will be erratic and slow. Hope this helps. 

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