Short stroking the impact

Forums PCP Airguns Short stroking the impact

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    bucketboy
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    Sub 12fpe impact have a different barrel port, hammer and hammer spring, yet the distance the hammer travels from trigger sear release to valve strike is the same as it is for high power monsters.  IMO opinion this makes the firing cycle slow and induces rattle and twangs as  the weaker hammer spring settles after are each shot. I also don’t like the amount of metal to metal contact in the hammer channel, the vibrations (and noise) drives me nuts, it can’t aid accuracy either, so I came up with this.

    new ptfe hammer guide, ptfe top hat to support the spring and stop the metal hammer becoming in contact with the valve stem. In addition there is a delrin insert into the nose of the hammer to reduce travel distance from 22.5mm down to 16mm,  the c3 bumper is still in use.

     


     

    I needed to add more hammer preload to make up for the shorter distance to attain enough speed to open the valve but the gun feels so much nicer and consistency is better, not yet been able to test for accuracy but I would guess it’s not made it worse.

     

    Bb

    • This topic was modified 1 month ago by bucketboy.
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    Hobbyman2007
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    Nice piece of kit there Bucketboy. I’m going to have a go at the hammer spring in my X model. Not for low power but to help with consistency. The hammer spring was not properly finished in my rifle with open ends simply cut , not flattened or ground flat. I took it out a while back and didn’t address the problem , to be honest I was disappointed that a 2000$ rifle would come like that. I’m sure you’d never see an HW100 with such poor QC . 

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    bucketboy
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    Hobbyman2007

    Nice piece of kit there Bucketboy. I’m going to have a go at the hammer spring in my X model. Not for low power but to help with consistency. The hammer spring was not properly finished in my rifle with open ends simply cut , not flattened or ground flat. I took it out a while back and didn’t address the problem , to be honest I was disappointed that a 2000$ rifle would come like that. I’m sure you’d never see an HW100 with such poor QC . 

    Thanks,

    I would definitely recommend the top hats at each end of the spring, the difference they make in holding everything central, reduces noise and vibration is very noticeably.

    Your right about the Q/C, I am slowly working my way thought the gun doing minor modifications to the parts as I go. The next thing on my list is to fit a LW barrel. For the power and pellets I use, I am not convinced by the liner system, too many parts, too many o rings,.  To be fair it shoots ok but needs cleaning way to often for my liking and before I even got the impact it was always my intention to fit a .20 barrel.

     

    Bb

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    Vana2
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    Great idea Bucketboy! Well implemented as well!

    Don't know if your improvements would apply to a standard FAC Impact or not but I hope that FX sees this post for the sub 12fpe guns.

    @hobbyman2007     Know what you mean about the HW100 – I have a pair of FAC power ones in .177 and .22 caliber, that are my favorite rifles.

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    Airgun-hobbyist
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    Spot on. Another well thought out innovation from bucketboy!  With the amount of plastic out of the front there you could probably not have to use that C3 o-ring now.  In my experimenting I found that a solid stop against the hammer stop end makes a very consistent shot string.  Alternatively, you make these pieces out of teflon so they have very little resistance on the valve stem rod to make the shot string even more consistent (to further benefit your shortened firing cycle).

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    Hobbyman2007
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    Airgun-hobbyist

    Spot on. Another well thought out innovation from bucketboy!  With the amount of plastic out of the front there you could probably not have to use that C3 o-ring now.  In my experimenting I found that a solid stop against the hammer stop end makes a very consistent shot string.  Alternatively, you make these pieces out of teflon so they have very little resistance on the valve stem rod to make the shot string even more consistent (to further benefit your shortened firing cycle).

    Yep that is just like my findings , a solid C3 or none all together make for a more consistent shot string. 

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    Airgun-hobbyist
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    @hobbyman2007  That spring you found  being unfinished on the ends produces side loading on the hammer weight and induces drag on the valve stem rod assembly at the shot.  Hopefully this was just a bad spring in the batch from the spring manufacturer that the FX assembly workers did not see.  It's hard to instill everyone to have the same high standards in life, and we have seen a bit of lack in QC from the line workers there lately.

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    bucketboy
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    Airgun-hobbyist

    Spot on. Another well thought out innovation from bucketboy!  With the amount of plastic out of the front there you could probably not have to use that C3 o-ring now.  In my experimenting I found that a solid stop against the hammer stop end makes a very consistent shot string.  Alternatively, you make these pieces out of teflon so they have very little resistance on the valve stem rod to make the shot string even more consistent (to further benefit your shortened firing cycle).

    Thanks,

    yeah I might (very nearly did) try it without the c3 bumper but I like to do just one modification at a time so I can see what improvements (if any) it has made.  Being that mine is sub 12fpe the c3 bumper doesn’t take the bashing you guys give yours, I only did one magazine’s worth over the chrono after setting it up and got 5fps spread which is a huge improvement from new. The gun is also 9.8dB quieter. 

    i shall be making a new piston from brass sometime soon, I am not a fan of a plastic piston, not only does it pressure form over time, it is heat sensitive so will change dimensions as temperatures changes. While this might not have much of an affect on its own, a 1000 small improvements make a big difference.

     

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