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Thread: Spring Gun Tuning

  1. #31
    Join Date
    Apr 2007
    Location
    Tulsa, OK USA
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    48
    thanks for the IPA tip... yes it's sold over the counter in USA for cheap.

  2. #32
    Join Date
    Sep 2004
    Location
    Colchester - Romano-Saxon Firearm EDties
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    4,256
    Quote Originally Posted by joekid View Post
    ... and good silicone oil (bisley) for poly seals(plastic type seals) ...
    No, absolutely not! Anybody who is using oil and especially silicon oil in the compression chambers of spring guns has been badly informed. Regards ... Geek
    PauL H. - Shotgoon
    Brownings: 1999 Ultra XS; 2004 B525 Field; 2010 Maxus Hunter: Air Arms 1998 Mk.2 Pro-Target, 2001 Mk.2 Pro-Sport & 2003 S400C

  3. #33
    Join Date
    Apr 2005
    Location
    Northampton
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    2,157

    Piston seals

    I do not pretend to be an expert, but the more rifles I strip and the more I read (particularly Cardew, the Airgun from Trigger to Target), the more I realise just how important it is to size the piston seal to the cylinder. The fit between seal and cylinder seems to be the major factor with older guns, in establishing the ME. I recently stripped and cleaned/relubed an old Meteor with an "O" ring seal and it did not occur to me to try and size the "O" ring. The "O" ring was in good condition and I gave it a smear of molypaste before reassembling. The gun is fireing fine but is low on power. The spring is fine and the relube is fine, therefore must be the seal! I cannot see a nitrile/butyl "O" ring sizing down very much and Ged Finn on another thread suggested possibly fitting a smaller diameter "O" ring. Presumably an "O" ring could be sanded down. The Cardew book demonstrates just how critical the sliding fit between seal and cylinder is, but unfortunately this is just guess work without equipment to measure the sliding fit. Too tight and you have limited power...too slack and you have the same result. The joys of springer tuning!

    Mike95

  4. #34
    Join Date
    Dec 2005
    Location
    Grantham Lincs
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    2,775
    Lower ME guns work better with parachute or semi parachute seals with sliding fit but FAC and higher ME springer's work more efficiently with higher swept volume solid seals with a tighter fit. Both need a good moly paste and a cross hatched compression wall to wet edge the seal to wall contact. It is not unusual to have a 30% range of power with the same spring set and different seals.

  5. #35
    Join Date
    Sep 2007
    Location
    monterey, california, USA
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    11

    HW80 hold sensitivity?

    Pardon the slight change of subject from strictly tuning, but I can't start a new thread.

    Got a HW80/Beeman R1 question if you would:

    Anyone have a 12 ft/lb HW80?

    I have a FAC R1 (am here in Calif, USA) that does 7.9 gr Crosman Premier Lites about 1,010 fps.

    Problem is, that though it groups accurately, it is hold sensitive in that if I switch from shooting standing with a rest, to sitting with a rest (artillery hold used both), the nice and tight groups move vertically.

    At about 35 yds, my sitting with rest groups hit about 1.5 inches higher than my standing w/rest groups.

    Can anyone comment on how a 12 ft/lb HW80 is about allowing different holds without the groups moving up/down?

    Power is nice, but accuracy is better.

    I'd get a 12 ft/lb kit for my Beeman R1 if that would make it more like my AA TX200 (which hits the mark, no matter how I hold it. Dittos for my Beeman R7 and HW55s).

    Oddly enough, my Beeman R9 is more tolerant of varying the way I hold it and does not shift the groups like my R1.

    Thanks, and good luck on keeping your airgun freedoms. Here in the USA we have the "Democratic" Party that would strip us of our firearms, airguns, water pistols, sharpened pencils, etc if they got the chance.

    Robert Hamilton
    California, USA

  6. #36
    Paul Hudson Guest

    To Robert Hamilton

    Hi Robert

    I found that dropping the power of a 12fpe HW80 down to 10.5fpe and using 7.9g pellets (Mosquitoes) made a huge difference. The rifle was much more tolerant of different holds, simply because it exhibited MUCH less recoil.

    Also, putting the action into a heavier stock further reduced recoil. It's the only 80 I've shot that let me keep the crosshairs on the target throughout the firing cycle.

    I've since sold the rifle to Adam77K on here, so it might be worth having a word with him...

    Paul.

  7. #37
    Join Date
    Feb 2004
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    Radcliffe on Trent ,nottinghamshire
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    how can you add some weight to your rifle stock with out ruining it .

  8. #38
    Join Date
    Sep 2007
    Location
    monterey, california, USA
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    11

    10.5 ft/lb M.E. HW80/Beeman R1?!

    Hi Paul,

    Thanks much for your reply. Non-hold sensitive R1 at 10.5 ft/lbs M.E.? Very interesting. And with the factory weight (heavy) piston at that! Imagine!

    I had a custom, lightweight piston made for my .177 FWB124 springer (factory piston: 10.5 oz & custom 124 piston: 8.5 oz), and put in a soft tune kit that had 7.9 gr JSB Exact Express 4.52 doing 770 fps (7.9 gr CPLites did 730 fps with same tune due to tighter fit). Hold sensitivity was reduced, but still had about 1" vertical difference between where the groups hit at 40 yds, sitting w/rest vs. standint w/rest.

    Do you remember how the R1/hw80 was at 12 ft/lbs ME? I'm not sure I have anything to drop my R1 down to 10.5 ft/lbs, but I do have an old Jim Maccari 13 ft/lb kit I might be able to use to get down to an even 12 or 11 via no spacing.

    Again, thanks for your comments.

    Robert Hamilton

  9. #39
    Paul Hudson Guest
    Hi Robert.

    At a shade under 12fpe it was tooth-jarring

    I dropped the power simply by shortening the spring slightly. I also sized the seal for a sliding fit - that is, the piston and seal would slide gently down the cylinder under its own weight, stopping if the transfer port was blocked.

    Darren - I fitted it in a Sono Kembang GinB stock which added nicely to the weight.

    However, one of my 97Ks sat in a brute of a walnut stock that I added around 5lbs of lead to - and you couldn't tell unless you tried to lift it . The simplest way was to fill a few lengths of 15mm copper water pipe with lead, drill a series of 15mm holes into the end of the stock under the butt pad, then slide the weighted pipes into place.

    Paul.

  10. #40
    Join Date
    Sep 2007
    Location
    monterey, california, USA
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    11

    hw80/Beeman R1 at 12 ft/lbs ME

    Teeth jarring at 12 ft/lbs? Well at about 17 ft/lbs, my R1 has a fast bit of kick. But with it moving groups vertically with differences in hold style, my R1 has been a closet queen.

    Thanks for the detune tips.

    I've been happy using my TX200's for small pest hunting at local farms/ranches. Got 54 California ground squirrels recently at a local cattle ranch. Rancher was going to poison them out (slow death by internal bleeding...takes 2/3 days to die sometimes), so I did my best to thin his pest population down to the point he doesn't go the poisoning route.

    Robert Hamilton
    Calif, USA

  11. #41
    Paul Hudson Guest
    Quote Originally Posted by rehmk5 View Post
    Teeth jarring at 12 ft/lbs? Well at about 17 ft/lbs, my R1 has a fast bit of kick.
    I found the HW80 to be a bit of an enigma

    At 17 to 18fpe they're sweet and smooth; at 12fpe they're "tolerable" but unpleasant. At 10.5fpe they become sweet and smooth again, and a genuine pleasure to use. With the lighter, 7.9g pellets, I was getting the same muzzle velocity as with 8.4g pellets at the higher power, so the trajectory and POI was exactly the same.

    Have fun with your tinkering

    Paul.

  12. #42
    Join Date
    Sep 2007
    Location
    monterey, california, USA
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    11

    hw80 power levels

    Well, thanks for sharing your HW80 experiences Paul.
    Much appreciated.
    Few in the USA have experience with the lower power levels.
    Robert Hamilton, Calif, USA
    (now back to reading the news about our idiot politicians)

  13. #43
    Paul Hudson Guest
    Quote Originally Posted by rehmk5 View Post
    (now back to reading the news about our idiot politicians)
    Nothing different on your side of the pond then either...

    Let us know how you get on with the 80.

    All the best,

    Paul.

  14. #44
    Join Date
    Dec 2005
    Location
    Grantham Lincs
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    2,775
    Just squeezed mine up to 23fpe and it's fantastic, a real self contained FAC air gun with enough power to be worthwhile. Over 900 fps with light pellets and 800fps with 16g.

  15. #45
    Join Date
    Feb 2004
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    Radcliffe on Trent ,nottinghamshire
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    e-sheep
    whats the accuracy / recoil like at that level .

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