Fx Impact Fix & Mods for more FPS / FPE

Forums PCP Airguns Fx Impact Fix & Mods for more FPS / FPE

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    heavy-impact
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    edosan

    Try the carbide burrs and you won't mess with grinding stones anymore.

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    Kikopower
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    Thank you all for your quick response. Heavy-Impact, those carbide burrs are exactly the same ones that I’ve got. I’ll follow your advise. Edosan, thank you for the input too.

    • This reply was modified 5 months ago by Kikopower.
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    edosan
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    heavy-impact

    edosan

    Try the carbide burrs and you won't mess with grinding stones anymore.

    I have and tried, I prefer the stones for that job. Both do the work tho.

    • This reply was modified 5 months ago by edosan.
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    ImpactHunter.
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    hello 

    I am just about to start to tuning my Impact.

      Does these dimensions stands for all cals?or just for 22?

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    heavy-impact
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    Just .22 for the ID.

    This porting gives the most gain in .22 caliber. Larger bores also benefit, just not as much as .22

    First seat a pellet before removing the barrel.

    Flare the brass port to 7.4mm at it's entrance

    Elongate the inside of the port getting close to the back of the seated pellet. The goal is to have a smooth radius that air can follow. Do not make the port wider or you can have feeding problems.

    Blend the flared area into the elongated portion so that all surfaces have a smooth transition.

    Enlarge the bottom hole in the pellet probe so that it's larger than the brass port. Knife edge the hole so that air crosses it smoothly.

    Remove the top of the pellet probe above the feed hole. Don't square the back edge or it won't feed smoothly. Knife edge the parts you ground so that air crosses them without turbulence.

    When done correctly the gun will feed any ammo the same as before modifications but you will get the same velocities with 20-30 bar less pressure in .22 caliber. The larger bores will gain performance but .22 gains the most.

    When going above 145 bar a 4 gram hammer weight is necessary but the gun gives better performance and less ping with the hammer weight at any pressure.

    Replace the C3 bumper with a Delrin washer.

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    Airgun-hobbyist
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    @impacthunter. Those images above, not the sizes, can be used to visualise the shape of the port your trying to achieve if you're porting a different caliber Impact than shown.  The one thing that you don't want to do is widen the port down by the bore at all.  The drawing's represent widening and elongating the outside and funnelling it down to the original drilled port and bore.  You can enlongate the port a little bit, but the gains are negligible since the port has been funneled like that.  The enlongated funnel shape created a Venturi and flows the air faster through the Venturi. 

    Here's my latest port job for the .30 caliber.  As you can see I did go into the back of the port a little, but I shaped it a little at a time while testing it with a slug and pellet.  If you get it wrong the pellet or slug will go nose first through the port hole and clip or jam.  Slow and steady wins the race. Trust your work and test as you go.

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    Airgun-hobbyist
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    @heavy-impact It looks like I was putting this together and taking pictures as you were posting!

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    ImpactHunter.
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    Thank you  heavy-impact and  Airgun-hobbyist for your response

    I read all the posts from the first to the last page,and since english is not my first language,there are a few

    things (words) that I dont understand.and even Google can not translate to me.

    I have Impact mk1 in 25 cal.I shoot only pellest for now.

    I want to tune it but before I start doing it I want to know every detail of it how to do it on the right way. Thanks to you all, I have a place where to learn

    I have replaced C3 bumper to Delrin,

    I bought two spare pellet probes,45 cc external plenum and 6.35 valve seat.

    heavy-impact

    Hamer weight I did not plan to use since I will not go above 130 bar reg pressure.But thanks for advice I will put some 4 gram

    One thing that worries me is BRASS transfer port and how to open (elongate) it properly.

    If I understand you well it is important that inside hole in the brass port where pellet slides to barrel must stay the same to avoid jam  issue?

    Airgun-hobbyist 

    The picture I found on the internet, if it is yours you did a excellent job

     
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    mtnGhost
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    edosan

    heavy-impact

    edosan

    Try the carbide burrs and you won't mess with grinding stones anymore.

    I have and tried, I prefer the stones for that job. Both do the work tho.

    Every carbide burr that I have used likes to grab brass material violently. Might be fine in a proper endmill and vise to lock the workpeice, but it's not worth the risks in a Dremel.

    • This reply was modified 5 months ago by mtnGhost.
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    edosan
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    Right! Is That + almost instant polish with stones. No need an extra polish. I just use the same one for it.

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    heavy-impact
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    mtnGhost

     

    Every carbide burr that I have used likes to grab brass material violently. Might be fine in a proper endmill and vise to lock the workpeice, but it's not worth the risks in a Dremel.

    Ya gotta work on that grip strength. 💪

    I never noticed any grabbing. I use a tight grip and light pressure with the carbide burrs. Lower speed helps control when your getting close to the final shape.

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    heavy-impact
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    ImpactHunter.

     

    heavy-impact

    If I understand you well it is important that inside hole in the brass port where pellet slides to barrel must stay the same to avoid jam  issue?

    Airgun-hobbyist 

    The picture I found on the internet, if it is yours you did a excellent job

    Where the pellet slides can not be wider or you will have feeding problems. Longer is Fine.

    The picture you found on the internet is mine.

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    marcobet38
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    HI..did anyone ever measure the diameter size of .22 pellet probe ?…i order complete barrel kit but the probe was missing when i received the package.. i  intend to lathe myself

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    edosan
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    mtnGhost
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    edosan

    Damn I had the same idea! I should really get a proper end mill 😭

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    heavy-impact
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    I don't think there will be any gain going above bore size on the port.

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    Vadimas
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    mtnGhost

    edosan

    Damn I had the same idea! I should really get a proper end mill 😭

    The dual port has a difference of 40fps from the standard port. so if you end up with an elongated port it makes no difference.

     

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    edosan
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    Is not only about getting more power, is about having 2 settings in one barrel. 

    It might have some good uses in fpe restricted competition. Changes on site.

    Dual can be elongated too (original vs elongated). 

    One more tool for more tweaking

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    Vadimas
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    edosanas

    Is not only about getting more power, is about having 2 settings in one barrel. 

    It might have some good uses in fpe restricted competition. Changes on site.

    Dual can be elongated too (original vs elongated). 

    One more tool for more tweaking

    Each weapon needs to be assigned its own pellet or slug.

    I only use slugs, and I adjust everything by one parameter.

    I choose the best BC and accuracy I always use one slug.

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    Airgun-hobbyist
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    heavy-impact

    I don't think there will be any gain going above bore size on the port.

    I think the gain is also from the pellet or slug not dropping off nose first into the port.  So with the center supporting the projectile you can get an even bigger port area on either side of that, essentially making the ports the perfect size for the air volume needed and  also contour shaping the port's exit into the barrel for optimal flow.  

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