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Thread: HW75 upgrade power ?

  1. #1
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    HW75 upgrade power ?

    Hi all,

    I read that it is possible to increase the power of the hw75 by adding a shim / washer behind the piston in order to reduce the compression chamber.
    What do you think?
    Thx
    Marc

  2. #2
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    you need to look at reducing headspace.. not much else is going to help, and I doubt there's much anyways.

    Buy an Alecto and go with 2 pumps if you want more power..
    Last edited by Shed tuner; 25-11-2020 at 09:54 PM. Reason: typo'd "doubt"
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  3. #3
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    I agree with the above... well apart from using the word "doubt" (incorrect spelling ) Just saying
    "Every silver lining has a cloud!"

    HW77K, Rapid 7 MKI . HW97Colt GC, S&W 686 (CO2) HW75 . HW100K FSB

  4. #4
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    You need to get more air in, not less.

    And you pretty much can’t.

    There’s a reason most reasonably-sized top-lever SSPs (FAS, Gamo, HW75, Nemesis, HW40) all make very similar power levels. It’s physics.

  5. #5
    Captain Bongo is offline I'm not falling for this again........
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    Quote Originally Posted by Marc of France View Post
    Hi all,

    I read that it is possible to increase the power of the hw75 by adding a shim / washer behind the piston in order to reduce the compression chamber.
    What do you think?
    Thx
    Marc
    I can see what you are thinking, it will increase pressure. But it will also reduce volume and I suspect the designers have already located the sweet spot. Of course, you haven't got anything to loose by trying it and reporting back to us.

  6. #6
    harvey_s's Avatar
    harvey_s is offline Lost love child of David Niven and Victoria Beckham
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    ....and for what exactly?

    Another few FPS ain't gonna make difference except making it a pig to cock.

  7. #7
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    You could try what I’ve always thought about trying with mine, but never got around to actually doing:
    Try swapping the barrel for a .22 version from an HW45. .22 is more efficient in a pre charged air gun and you might get a small gain from it?

  8. #8
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    Quote Originally Posted by Andy W View Post
    You could try what I’ve always thought about trying with mine, but never got around to actually doing:
    Try swapping the barrel for a .22 version from an HW45. .22 is more efficient in a pre charged air gun and you might get a small gain from it?
    i think the 75 barrel is actually longer than the 45.. but yes, a .20 or .22 might give a fraction more - but not much; the volume is low, so the pressure drop off is sharp..
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  9. #9
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    I should give it a try, I have everything I need to hand; HW75, HW45 & CB625 to check it after the swap. But I just never get around to it. My enthusiasm for tinkering around with air guns seems to have evaporated in the last 5 years.
    Interesting point about barrel lengths being different though. I didn't know that.

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