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Thread: Had some interesting chrony results...

  1. #1
    REP: The Airgun Shop

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    Default Had some interesting chrony results...

    About a year ago and after about 12000 shots I decided to give my BSA a bit of TLC. I polished everything on the inside, put in a different (smaller) spring, new seals, etc. Up to 50m it is as accurate as any other springer I've used so far. Lock time is very quick, and the rifle is very consistent. This weekend was the first time I ever chronied it. Power is lower than I thought it would be, but it doesn't matter. Chrony string showed an average of 698 ft/s, but the difference between highest and lowest were only 3,5 ft/s !!!

    But the biggest surprise of all was Stefan's QB78.
    10 shots showed 2 ft/s from high to low, with average of 664 ft/s.
    Not bad for a stock standard CO2 rifle!!!!
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  2. #2
    Sharp Shooter

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    Dit klink meer na n pee-shooter...
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  3. #3
    Sharp Shooter

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    Did you wash/sort the pellets before the crony tests?
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  4. #4
    REP: The Airgun Shop

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    "wash/sort the pellets before the crony tests" WTF ?????

    I dropped the Airvolution magazine a few times in the sand, and still kept on shooting. Some guys were joking about it saying that it is not an AK47, etc.
    You really think I will bother with sorting pellets?

    I used JSB's. For the price they better be washed, sorted and polished.

    Ian, that peashooter can kill a pigeon with a headshot at 50m. Check jou mail...
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  5. #5
    Protea FT Team '12

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    Hoe gaan dit met die Airvolution? All enige chrony werk daar gedoen?
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  6. #6
    REP: The Airgun Shop

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  7. #7
    Sharp Shooter

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    Farmer, can you give me an advice, what did you use to lubricate the BSA, after stripping and polishing?
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  8. #8
    Sharp Shooter

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    Vaseline and Curry Powder...... Check our reply's in your other post....
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  9. #9
    REP: The Airgun Shop

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    Red Rubber grease on the springs, Pelgun oil on all the other small parts and seals.
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  10. #10
    Inactive Member

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    Farmer What or where is the airgun shop? Have you just changed the name?
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  11. #11
    REP: The Airgun Shop

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    Click on the thing !!!
    We will hopefully be in the position to open the shop soon. At the moment if have to be online cause we don't have anyone to work there fulltime.
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  12. #12
    Sharp Shooter

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    nice
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  13. #13
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    For testing consistency, you have to use weighed and sorted pellets.
    Pellets straight from the tin can give very erratic readings, purely due to the variation in manufacture of the pellets themselves.
    A typical ten-pellets from a tin of JSB's would weigh something like:

    8.2
    8.3
    8.4
    8.4
    8.4
    8.5
    8.5
    8.5
    8.6
    8.7

    A larger sample would find a few outside of the 8.2-8.7 grain spread.

    If your gun was to fire both the 8.2gr and the 8.7gr pellets at exactly the same muzzle energy of 11.3ftlb, the 8.2 would come out at 788ft/sec, while the 8.7 would come out at 765ft/sec.

    The difference would be 23ft/sec, even though the gun was perfect and had no variation in muzzle energy.

    So a sample of unsorted pellets can easily give a spread of 20ft/sec in .177. And the more shots you fire, the more likely you are to get a rogue reading - it's the laws of probability and the Gaussian curve.

    Once you start using weighed and sorted pellets, you'll get much tighter velocity spreads.
    An outstanding gun will manage +/-0.25% velocity variation (+/-2ft/sec).
    A good gun will manage +/-0.5% velocity (+/-4ft/sec).
    An average gun will manage +/-1% (+/-8ft/sec).
    ...and a spread of up to +/-1.5% (+/-12ft/sec) will be accurate enough for most people.
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  14. #14
    Inactive Member

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    Very nicely put Gerrief...
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  15. #15
    Inactive Member

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    Thanks!!
    "At normal airgun ranges the variation fps on POI isnt going to be noticed by an average shooter. Even decent shots would probably find it within "tolerance"

    It takes ages for a shooter to find the right combination of pellet, lube, cleaning...................theres a whole list of things you got to do to get little lump of lead to land roughly where you want it to and fps, as it goes, is not going to mean your knob is going to drop off just coz its 15fps as opposed to 2 fps.

    Are you telling me your going to be bothered if your pellet hits 4 mm above or below each other - if we use Fluffs figures as a bench mark.

    draw an 8m circle and see if you wouldnt be happy with a group that size.

    You will do more to cock up a shot than a few fps ever can so unless you vice it in a bench rest and take out all the other miriad of variables that happen in the process, I doubt you'd even realise what fps your kit is doing in terms of variation unless your gun was axtra sick."
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