Fx Impact Fix & Mods for more FPS / FPE

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

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    Airgun-hobbyist
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    edosan

    heavy-impact

    Chris1973

    That’s why I ask. As I see od 50 mm  id 40 mm that means 10 mm walls. Right?

    5mm walls

    Miss that q. Thanks my friend!

     

    PaniSd

    @edosan … I have already half moon shape, so I done this one. You didnt notice at the end of video.

    Ohj sorry for that, got a phone call just before that part, 👌💪✌

    I did this too, but opened up a more on the top and sides for air expansion.  It didn't seem to change much in the way of FPS, as I had already ported and polished the block and transfer ports, as well as the valve housing.  But I'm sure that it is a bit more efficient in the flowing of air around the bend into the brass transfer port.

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    mtnGhost
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    Well I scrapped the one that I had deleted the bottom half of. It was loading slugs just fine, but I had some loading problems with pellets! I reverted to using the first one that I double ported, expanded both ports a little and I'm not seeing any differences in velocity / accuracy with any of the 3 modes probes 🤷‍♂️ 

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    ackuric
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    mtnGhost

    Well I scrapped the one that I had deleted the bottom half of. It was loading slugs just fine, but I had some loading problems with pellets! I reverted to using the first one that I double ported, expanded both ports a little and I'm not seeing any differences in velocity / accuracy with any of the 3 modes probes 🤷‍♂️ 

     

    What fps are you shooting at,  if you're far enough from the knee or plateau I can see there being no noticeable gains.

     

    -Matt

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    jp003
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    Few mods to my new MKII Impact. Reg pressure 140 

    Changed C3 bumper to delrin, increase speed 25-30 fps

    Enlarged barrel tp hole and cut off section of the pellet probe 

    Pellet probe design one, increase speed 40-45 fps

    Pellet probe design two, increase speed 50-55 fps!!! ( I thought design one will give more speed, but I was wrong.)

    Now I can shot JSB .22 redesigned  consistently around 993-998 fps!  Will do more test with other calibers.

    • This reply was modified 6 months ago by jp003.
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    Scotaty
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    jp003

    Few mods to my new MKII Impact. Reg pressure 140 

    Changed C3 bumper to delrin, increase speed 25-30 fps

    Enlarged barrel tp hole and pellet probe 

    Pellet probe design one, increase speed 40-45 fps

    Pellet probe design two, increase speed 50-55 fps!!! ( I thought design one will give more speed, but I was wrong.)

    Now I can shot JSB .22 redesigned  consistently around 993-998 fps!  Will do more test with other calibers.

    Looks good, 600mm or 700mm?

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    heavy-impact
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    jp003

    Few mods to my new MKII Impact. Reg pressure 140 

    Changed C3 bumper to delrin, increase speed 25-30 fps

    Enlarged barrel tp hole and pellet probe 

    Now I can shot JSB .22 redesigned  consistently around 993-998 fps!  Will do more test with other calibers.

    You can get a little more by flaring the entrance of the brass port. The port that feeds it is a little over 7mm. This also prevents any port alignment issue.

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    jp003
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    @scotaty…it’s a 700mm barrel

    @heavy-impact…thanks for the info.  I don’t know the size of the port feeding the barrel.  If it’s little over 7mm ,I’ll flare the opening of the barrel more to cover that port.

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    Chris1973
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    Heavy impact 

    thank you for the correction 

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    Chris1973
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    Airgun hobbyist thank you as well for the correction. That’s why I like this forum. You can not go wrong! Someone will notice for sure the mistakes ! 👍🏻 

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    mtnGhost
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    ackuric

    mtnGhost

    Well I scrapped the one that I had deleted the bottom half of. It was loading slugs just fine, but I had some loading problems with pellets! I reverted to using the first one that I double ported, expanded both ports a little and I'm not seeing any differences in velocity / accuracy with any of the 3 modes probes 🤷‍♂️ 

     

    What fps are you shooting at,  if you're far enough from the knee or plateau I can see there being no noticeable gains.

     

    -Matt

    I was originally measuring with the short 380mm barrel with medium power settings in my Crown, where my double ported probe was shooting the 25gr JSB Monster RDs around 860. The two modded probes with the same tune raised velocity to 880-890, where the one with the deleted bottom part shot consistently at 885.

    When I turned up the power, my original was steady at 935fps, and the other two were shooting in the low 940s (with slightly erratic SD from 935-948). I'm focused more on eliminating deviation and spread than trying to rice a few extra fps, but I might revisit this if I decide to shoot 38-40gr.

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    heavy-impact
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    jp003

    @heavy-impact…thanks for the info.  I don’t know the size of the port feeding the barrel.  If it’s little over 7mm ,I’ll flare the opening of the barrel more to cover that port.

    When you just start to break the edge of the closest o-ring groove you're there.

    Where a port connects two bores it's diameter will be the minimum thread diameter of the plug under it. In this case 7.25mm for the M8x1.25 grub screw that also locks the valve housing in.

     

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    Airgun-hobbyist
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    JP003, When "flaring" the opening think of how a carburetor's Venturi works.  What is key is air will increase velocity as it is necked down, as is the principles of the Venturi.  So you are in essence making a Venturi in the brass transfer port that matches the port in the rear block.  Another thing that helps the flow is to not let air make a square 90° turn.  Break the edges down at the turn so it looks like it will "flow" into the barrel smoothly.  The end goal of porting is to make the air move through the valve housing, into the block, and through the brass transfer port as smoothly as possible, without air having to make sharp bends and pass over "ledges" where the ports don't match up; in effect, one smooth transition from the valve housing into the barrel.

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    jp003
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    @airgun-hobbyist, thanks for the detailed explanation!👌

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    edosan
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    Guys, you have no idea on how happy this make me feel … collective knowledge to get us improved! Awesome !! 

    BTW, Real test on Fatboy (that is  what I call my new plenum), and 3rd place 50m, no 75! my specialty damn!) in this sunday competition, not too bad for fatboy new born! jaja it was a fun comp, but next sunday will be the real test, Here some pics.

     

    • This reply was modified 6 months ago by edosan.
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    heavy-impact
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    Congratulations on another win. Is the fat boy plenum 60 x 80mm ?

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    edosan
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    heavy-impact

    Congratulations on another win. Is the fat boy plenum 60 x 80mm ?

    Podium (3rd place) no win! but THANKS! ;)

    This looks familiar to you?

    :D

    • This reply was modified 6 months ago by edosan.
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    heavy-impact
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    edosan

    heavy-impact

    Congratulations on another win. Is the fat boy plenum 60 x 80mm ?

    Podium (3rd place) no win! but THANKS! ;)

    This looks familiar to you?

     

    :D

    Got it, I thought you might have made a larger one.

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    edosan
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    no, no need to make it even larger (for now jajaja) I want to test the bore dimensions now.

     Ernest is 40mm OD

    • This reply was modified 6 months ago by edosan.
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    edosan
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    Raw material 😉

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    mtnGhost
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    edosan

    Raw material 😉

    OoOoh.. what have you there??

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