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Thread: BAM pcp fill pressures

  1. #1
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    Default BAM pcp fill pressures

    After having a little trouble with my BAM out of the box (it wouldn't fire when filled to 200MPa), I have been doing some research and also personally experienced that filling to 200MPa with these guns is a waste of air.

    Those that fire at 200MPa out of the box, end up firing at very high velocities as the pressure drops to 150Mpa and below. This is OK if shooting at targets at 10m, but at greater distances you need to be shooting in the "sweet spot" for any consistent accuracy.

    The guys on the yellow forum (Rich, etc) who arguably pioneered the power tunes for these guns, all fill to much lower pressures and still get decent shot counts.

    I find that personally I seem to get the best results with mine if I fill to only 160MPa, and I still get 100 shots at 10m distances. I reckon at greater distances I would get only 40-50 usable shots before a refill, and any shots at fill pressures between 160 and 200MPa would be way inconsistent with those between 160 and 100MPa.

    I guess then I should not have been concerned about my BAM not firing at a 200MPa fill, as it fired OK when I dropped the pressure to 160MPa and that seems to be where the "sweet spot" starts anyway.

    BTW my BAM has a 1.4mm transfer port and I fitted an allen key grubscrew to adjust the power through the safety catch screw hole (thanks Wyan!). If I adjust the power so it fires at 200MPa its too powerful in the "sweet spot". If I adjust the power down with the screw it doesn't fire at 200MPa, but I don't think it is anything to be concerned about.

    Has anyone had similar experiences?

  2. #2
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    ---------------------------------------
    Quote Originally Posted by huffnpuff
    it wouldn't fire when filled to 200MPa
    ---------------------------------------



    hehe...obviously u meant 200bar. becoz 200MPa = 2000bar.

    better consistency and more shots count will be next tuning work on my BAM51 hunter project.




    <span class='smallblacktext'>[ Edited Fri Mar 03 2006, 08:31PM ]</span>

  3. #3
    MOT: Thomson Pneumatic Rifles

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    60 shots at +-790 max 17fps exstream spread, 195bar fill to 150bar 45bar air on 60+ shots.

  4. #4
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    Hi I have also got a BAM 50 and I have seen with mine that filling it to 175 bar and shooting to 100 bar gives me the best results. I fire about 40-43 shots that are very mutch in the same hole at 35m and up to 55m I get good 4 shot groups. I don't know the speeds but the gun groups good with Barracuda Match 10.79gr 4.50 headsize pellets.


  5. #5
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    I got this reply from Rich on the yellow forum, he has put in a lighter hammer in his B50, this is what he had to say:

    "my B50 might lock up with 3000 PSI in it!
    I've been using about 1800 PSI (IIRC) and get
    a bunch of shots! Indoors, I don't notice any
    drop until I get up around 100 shots..
    At 30 yards, I don't shoot but 40 or 50 before refilling..

    There really isn't any need to fill to higher pressures,
    if the gun gives me a lot of good shots at low (and very low) pressures. The nice thing about low pressures is, it' easy to pump it up.
    If I got the same power and number of shots at 3000 psi,
    I wouldn't like it as much as using low pressure..
    The valve may actually work better when under less pressure. The USFT uses a BIG air tube and runs low pressure too."

  6. #6
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    Hi Boondock,

    Sorry, I did mean 200 bar or 20MPa, I keep confusing the 2, its probably better if I write these posts with my equipment in front of me so I don't try and work from memory (must be an age thing or cellphones have fried a few brain cells...or maybe too much heavy metal in my youth...?)

    cheers
    Martin

  7. #7
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    Huffnpuff,
    Or Klippies at our old age?

    Klippies and Coke, that is

  8. #8
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    Aaaah, that must be it, but in my younger days it would have been excessive Martell 5 Star, my tastes have changed of late...eeeish...

  9. #9
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    Chevas?

  10. #10
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    Me hailing from the same era as you guys with the one exception that I progressed to Olof f Bergh these days. I however lost you when you talk about different number of shots at different distances due to different pressures. Are you saying that you have more pellet drop on longer distances and therefore you get less accurate shots? Have I confused myself even more?

  11. #11
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    I found out what the problem was with some of the guns not firing above 160 bar. They have heavier striker valve seal springs, so its harder for the hammer to hit the valve open.

    They fire OK below 16MPa (about 160 bar) until about 10MPa. The change in spring weight has just shifted the power curve to a lower pressure. I also noticed that on the models with the heavier spring, the brass ring around the striker valve seal is half as thick as the ring on the other guns, probably to reduce the preload on the spring.

  12. #12
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    Hi Gerrief

    At 10m, the change in point of impact with varying pressures is much less noticeable than at 30m. Therefore you get more useful shots to (more or less) the same point of impact at 10m than you would at 30m.

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