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Thread: Why is the HW95 so bouncy??

  1. #106
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    Quote Originally Posted by TonyL View Post
    According to Bruce's thread in the Useful Tips / Info section, the 95's piston comes in at approx 254 grams, Max.

    Dearne75 - sounds nice; be interesting to hear your thoughts after some more extensive testing.
    I've got the HW95 piston assembly at 270g, Tony.

  2. #107
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    Quote Originally Posted by maximus View Post
    Quite a weight reduction then, you'd think there would be more bounce to combat.
    Quote Originally Posted by BTDT View Post
    I've got the HW95 piston assembly at 270g, Tony.
    Yep, a pretty significant weight reduction indeed, Max. Even more looking at the information as provided by Jim. Thank you, Jim.

    As we've always said, it's all down to that question of balance......transfer port size and the choking effect, spring rate, preload, pellet start pressure, piston weight, piston momentum, cross sectional density etc. And will the longer stroke be more efficient, giving that longer power pulse? Short stroke will reduce the first phase of recoil displacement (also dependant on other factors) but, depending on that set-up, could result in harsher piston bounce and higher cylinder temperatures. To a degree I think we all like to sing a different tune and if the result is pleasing, accurate and usable, then it's job done?
    THE BOINGER BASH AT QUIGLEY HOLLOW. MAKING GREAT MEMORIES SINCE 15th JUNE, 2013.
    NEXT EVENT :- May 4/5, 2024.........BOING!!

  3. #108
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    Well, I just need mine to finish up at the "pleasing and accurate result" bit! The good news is that the chronograph seems to of sprung back into life so once the rain stops ill have another bash. Would be interesting to try a tx mk3 spring in it.
    Plinkerer and Tinkerer

  4. #109
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    Great to hear that the chrono is, hopefully, okay.

    I can think of many much worse ideas than trying the TX Mk 3 spring.
    THE BOINGER BASH AT QUIGLEY HOLLOW. MAKING GREAT MEMORIES SINCE 15th JUNE, 2013.
    NEXT EVENT :- May 4/5, 2024.........BOING!!

  5. #110
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    Quote Originally Posted by maximus View Post
    Hi, sounds great, what was the weight of the piston prior to machining?

    Also, how much pre-load with the vortek kit?

    Thanks Max
    There was about 25mm pre load with the vortek spring and standard seal.
    With the new short stroke seal it will be a furthur 10mm -thats the extra length of the seal to give about 35mm.

  6. #111
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    Quote Originally Posted by TonyL View Post
    According to Bruce's thread in the Useful Tips / Info section, the 95's piston comes in at approx 254 grams, Max.

    Dearne75 - sounds nice; be interesting to hear your thoughts after some more extensive testing.
    Yes its range time i need but 19yds in the garden will have to do due to covid19!

  7. #112
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    19 yards as a home range isn't exactly shabby, though.
    THE BOINGER BASH AT QUIGLEY HOLLOW. MAKING GREAT MEMORIES SINCE 15th JUNE, 2013.
    NEXT EVENT :- May 4/5, 2024.........BOING!!

  8. #113
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    Quote Originally Posted by dearne75 View Post
    There was about 25mm pre load with the vortek spring and standard seal.
    With the new short stroke seal it will be a furthur 10mm -thats the extra length of the seal to give about 35mm.
    Thanks for that, must be a softer spring than the std hw one I'm running unless the seal is a bit tight. I am also on a new std HW seal and its very free moving.
    Plinkerer and Tinkerer

  9. #114
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    Quote Originally Posted by BTDT View Post
    I've got the HW95 piston assembly at 270g
    In an old AGW, I think the article was about short stroking, there is a picture of you Jim, where you have a pock holed 95 piston sitting on a set of scales, I can't remember the weight of this piston off the top of my head, I think it was a lot less the 270g, did you abandon the lightened piston and go for reverse engineering upping the weight or is 270g the standard 95 piston weight ?

    ATB

    John
    Hw77+7

  10. #115
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    So we still haven’t resolved this.

    I had a theory that the 85/95 had an unusually long stroke (81-85mm?) combined with a heavyish piston.

    But that doesn’t seem to work. The D34 has 80mm or more depending on the piston/trigger group fitted.

    The FWB Sport is 77mm, but with a 304 gm piston.

    Maybe the HW hits a particular odd un-sweet spot where the piston is the wrong weight, the 12 ft-lbs spring is too slow, and the stroke at 12 ft-lbs is too long. Whereas the Diana and FWB avoid that through slight but important variations, including the famously heavily pre-loaded spring in the FWB?

    My other theory, given my dislike of the 85/95’s handling, is that it’s unusually muzzle light. Except, compared to an FWB, D34, let alone a B55 or a Vulcan, it’s not. Once you get the bloody thing on target, it stays firmly there, until it fires.

    It’s a mystery. One for the airgun X-files.

  11. #116
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    Quote Originally Posted by Geezer View Post
    So we still haven’t resolved this.

    I had a theory that the 85/95 had an unusually long stroke (81-85mm?) combined with a heavyish piston.

    But that doesn’t seem to work. The D34 has 80mm or more depending on the piston/trigger group fitted.

    The FWB Sport is 77mm, but with a 304 gm piston.

    Maybe the HW hits a particular odd un-sweet spot where the piston is the wrong weight, the 12 ft-lbs spring is too slow, and the stroke at 12 ft-lbs is too long. Whereas the Diana and FWB avoid that through slight but important variations, including the famously heavily pre-loaded spring in the FWB?

    My other theory, given my dislike of the 85/95’s handling, is that it’s unusually muzzle light. Except, compared to an FWB, D34, let alone a B55 or a Vulcan, it’s not. Once you get the bloody thing on target, it stays firmly there, until it fires.

    It’s a mystery. One for the airgun X-files.
    In my case i have a .22 hw95 which was fine out of the box and an hw95 .177.
    I got the chance to shoot a .177 at the range.It was superb,the lad told me wonky donky had tuned it.
    A while later i contacted WD about tuning my .22 and he spoke of a re-engineered tune like the rifle i tried at the range.The gun shoots brilliantly -a keeper.
    For the .177 i decided to try a few thing for myself which i have done,this weeks short stroke piston seal on a lighter hw piston being the latest.
    I believe lighter piston,short stroke with a good spring and good fitting guides is the way to tame this jumpy gun with a bit of weight to the silencer too.

  12. #117
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    Is there a nice slim silencer to put on? Presently have the factory HW unit which does the looks no good at all.

  13. #118
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    Quote Originally Posted by maximus View Post
    Quite a weight reduction then, you'd think there would be more bounce to combat.
    counteracted by the stroke reduction....
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  14. #119
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    Quote Originally Posted by HW55T View Post
    In an old AGW, I think the article was about short stroking, there is a picture of you Jim, where you have a pock holed 95 piston sitting on a set of scales, I can't remember the weight of this piston off the top of my head, I think it was a lot less the 270g, did you abandon the lightened piston and go for reverse engineering upping the weight or is 270g the standard 95 piston weight ?

    ATB

    John
    I'll need to plough through my old articles and notes to be certain, John, but I do remember first reducing the weight to match the sectional density of my 25mm HW77 (249g, being piston, seal and top hat), then taking it down to 238g.

    My conclusion was that, to reduce recoil, reducing piston weight was preferable to reducing piston stroke.
    Last edited by BTDT; 21-01-2021 at 06:07 AM.

  15. #120
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    Quote Originally Posted by Muskett View Post
    Is there a nice slim silencer to put on? Presently have the factory HW unit which does the looks no good at all.
    I bought one of DM80's slimline steel silencers to go on my HW95K to add some weight and it looks way better than the HW version. In essence it looks just like one of the old Venom silencers.
    People who have been there focus on the fundamentals. People who sit at keyboards all day focus on the trivial and inane.

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