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Thread: Spring gun tuning

  1. #1
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    Spring gun tuning

    I am currently tuning a HW85
    From memory years ago when I last did this, one secret was to open up the transfer port slightly to I think 1/8th inch, the idea was to reduce recoil but not increase power.
    Also the transfer port on my HW85 is at an angle upwards, which I do not remember from previous guns.

    Any help or coments would be welcome.

    Out of interest I await a Venom kit with new spring , guides etc

  2. #2
    Hsing-ee's Avatar
    Hsing-ee is offline may also be employed in conjunction with a drawn reciprocation dingle arm, to reduce sinusoidal repleneration
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    The transfer port size is critical and it's best to leave it alone. Once you have modded it it is very difficult to put right again. Best leave this sort of thing to the likes of Gerald Cardew and the Venom team.

    Just fitting the Venom kit will give a greatly reduced recoil on its own. Get the rifle Lazaglided rather than tinker with the 'port. If you do intend to go ahead with a port mod, read G.Cardew's The Airgun from Trigger to Target and his earlier one to The Airgun from Trigger to Muzzle first and get some advice from Venom or John Bowkett or David Welham at Airmasters.

    In the 70s I remember people opening up the transfer ports on HW35's to 4mm in the hope of more power.... most times it increased the recoil, reduced the power and knackered the accuracy. Proceed with caution, especially with a good, scarce rifle like the '85.

    Hope you like the sight!
    Last edited by Hsing-ee; 14-06-2004 at 10:09 PM.

  3. #3
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    Good advice that -don't mess with the port - the most I might be tempted to do would be to remove burrs, but make sure you understand your rifles action before doing anything that can't be quickly and easily reverted back !
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  4. #4
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    I've opened them to .1195" using a decimal size reamer, and it usually fetches about 15 fps more, combined with a careful chamfering of the rear of the transfer port. This represents just a .0015" increase in diameter to the port (one and a half thousandths of an inch) as the US FAC ports are 3mm (.118). Going to .125" (1/8") may be a 'bridge too far'
    The chamfering or light radiusing of the rear port.... 1mm to 1.5mm around the hole is fine. Chamfering can raise a burr that constricts the hole slightly (especially if the tool is a tad dull or the 'operator' applies too much pressure) so I usually follow up the chamfering with a decimal reamer the same exact size as the t port hole to clean any possible burr away. Good luck. RB
    PS: if you're running a 12 ft/lb gun and it's very close to the limit; I do NOT recommend increasing the port size!

  5. #5
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    Quote Originally Posted by two screws View Post
    I am currently tuning a HW85
    From memory years ago when I last did this, one secret was to open up the transfer port slightly to I think 1/8th inch, the idea was to reduce recoil but not increase power.
    Also the transfer port on my HW85 is at an angle upwards, which I do not remember from previous guns.

    Any help or coments would be welcome.

    Out of interest I await a Venom kit with new spring , guides etc
    Where have you heard that to open the transfer port will reduce recoil?,, How big is the transfer port now? BUT I would put the new kit in first AND SEE HOW THINGS GO,,

  6. #6
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    'Blast from the past' post of the day!

    I cant ever remember Steve (TWO SCREWS) having a HW85.

    ATB
    Ian
    Founder & ex secretary of Rivington Riflemen.
    www.rivington-riflemen.uk

  7. #7
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    Quote Originally Posted by I. J. View Post
    'Blast from the past' post of the day!

    I cant ever remember Steve (TWO SCREWS) having a HW85.

    ATB
    Ian
    WELL he might still have it I would like to know if he did get the drill out, and the out come

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