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Thread: Accuracy

  1. #1
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    Default Accuracy

    I would like to hear your various opinions on the causes of inaccuracy in air rifles. That is now not talking about the abilities of the shooter, pellets and weather conditions. What I am interested in is stuff like for instance how would barrel length affect accuracy - is a longer barrel automatically more accurate than a shorter one? How about thickness of the barrel? What about stuff like seals? In springers, what about the weight of the piston? I would appreciate your comments.

  2. #2
    Marksman
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    sheeshhh...you ask easy questions Kobus...the answer would fill a whole book.
    I advise you to start reading all the forums and all the relevant threads in them...all will be revealed.

  3. #3
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    Kobus , Guido is right . There must be many millions of words written about accuracy . There are many many factors that can affect a weapons accuracy .

    Barrel crown , rifling type , twist , protectile weight & shape , barrel length , with millions of variables thrown in .

    Then again you just get dud guns too , you try every thing & it just scatters them .

    Many years ago when I was shooting for Natal Combat rifle , we were given a trommel full of brand new weapons to check . I was absolutely stoked , I found an R4 that grouped inside an inch with iron sights at 100m . What I did'nt know till a competition 2 weeks later was that this same rifle couldnt get 10 shots on the board at 300m . There is a technique used by combat shooters , where , with a powerful spotting scope you actually watch the vapour trail go down range & you can tell the shooter within an inch where he hit the target 300m away .

    Well , I got a coach to watch my shots & we were absolutely gobsmacked how they spread in all directions down range ! We dumped that gun in a hurry , great for patrol work , but useless for competition . Lots of theory about harmonics etc etc .

    Odd , but as I said earlier , you just some times get dud guns .

  4. #4
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    And here I was thinking I am going to get an easy answer handed to me on a plate by the masters!! You guys realise that you are now putting unnecessary strain on my diminishing available grey matter. I was actually trying to cut down on internet time as well, but you leave me no option....

  5. #5
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    Second thoughts. Gerry, your reference to "dud guns" is actually exactly what I am looking for - what makes a dud gun? But I suppose Guido's answer will still apply, and the number of combinations of possible causes could be enough to make Einstein struggle.

  6. #6
    Sharp Shooter
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    Longer barrel, more accurate, the pellet has a longer guidance being directed to the target. a longer barrel also give you more rifleing, so you can get a good spin on the pellet to stabalise it.

    thinker barrel should be more accurate.... when you shoot a rifle, it vibrates like hell and if you watch a slowed down vidoe clip of the barrel as it fires, you will see how its twists as you shoot. therefore a thicker barrel should keep more stable... i know its little in pcp's, but there is a degree still there.
    look a the olympic rifles, all bull barrels...

    seals are important, something that doesnt seal 100% will give inconsistant shots and wont be ifficient due to loss of air out the chambers.

    in a springer, the heavier the pistol i think the worse, there will be more of a recoil, therefore flicking the gun around like they do.

    any others?


  7. #7
    Marksman
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    sorry...longer barrel is not more accurate by any means...
    There are a lot of other factors to be taken into account.
    In fact a longer barrel means more barrel time for the projectile, thus more time for it to be influenced by the shooter flinching etc...this is especially true in airguns.
    A 9 inch barrel like on the ProSPort is as accurate as a 24" barrel on a long PCP.
    Steyr barrels on all their match air rifles are 16" while the FWBs and Anschutzes have longer barrels.
    Match air pistols have 6 to 9 " barrels and all shoot thru the same hole at 10M.
    The quality , spin rate of rifling, number of lands and especially the crown are very important.
    Thicker barrel can be more accurate over the same thinner barrel but harmonics come into play too.

    Piston weight is also a trade-off...too light and the rifle will be harsh to shoot and twang a lot.
    Too heavy and the recoil will be quite heavy....

    this is going to be a long thread.....

  8. #8
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    He he he, the answers are coming in!

  9. #9
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    IIRC, in the Airgunners bible, it mentions that a longer barrel will require less air to achieve the same power as compared to the same shorter barrel. There is more time spent in the barrel to continue accelerating it. In the next paragraph they deny that accuracy is better in the long barrel. I think they did tests up to 25" lengths. Basic summary is along the lines of 'so long as the pellet has enough time in the barrel to create it's spin that is all that is required.'

    So perhaps the shorter 'lock time' on the carbines is a benefit since the human error is ever-so-slightly decreased.

    ...

  10. #10
    Marksman
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    this is only the case in PCP rifles...to get max velocity you need longer barrels.
    In springers the pellet is accellerated to max velocity in the first few inches

  11. #11
    Sharp Shooter
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    new someone was going to argue with that comment on the long barrel story....
    i would like you to show me that guido... because i have seen it been prooved many a times....
    anyhow, you cant use the excuse that their is more time for the shot to be flintched of coarse, because thats the shotists fault.... not the long barrel....
    tell me why something like a 4 inch barrel on a revolver shoots less accurate then a 10 inch barrel?
    Why dont they make .22 rimfire walther olympic rifle with short barrels if they are more accurate....
    Balls.... :boo:
    <span class='smallblacktext'>[ Edited Fri Mar 11 2005, 07:28PM ]</span>

  12. #12
    Marksman
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    Jason...if you talk about a 4" revolver that is a different story altogether...and normally the longer barrel revolvers are more accurate because of the longer sight line.
    After a certain length it becomes irrelevant.
    You have only seen it been proved with pistols and revolvers, not rifles I am sure.
    Olympic rifles don't have particularly long barrels, the reason they look so long is because of the bloop tube which is used to extend the sight line.

    Anyway in air rifles the longer barrel theory definitely does not hold true...especially after 9 inches or so...the pellet is spinning and has reached max velocity already..the important thing is as it leaves the muzzle the crown must be perfect to take it on a straight and true flight


  13. #13
    ice's Avatar ice
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    Jason the above have nothing to do with the lenght of the barrels, it down to distance between front and rear sights! The longer barrels have sights further apart which would aid in aiming.

    Keeerpow!

  14. #14
    MOT: Thomson Pneumatic Rifles

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    Hi Guys, here is my 2 cents worth. Long barrels are not inacurate. 10m Match rifles have short barrels to remove a smuch human error as posible not because the shorter barrel is less accurate. Rifling has a big impact on air gun accuracy, this knowlage was obtained not just be reading and surfing the net but through actual tests I have been conducting in my research, before building my own rifles. Twist rate is a big factor as slower heavier pellets (we are only talking .177 here as caliber goes up twist rates decrease, generaly speaking), require a higher twist rate as they travell slower, all things being equal. Also the desterbance of the lead on the pellet by the rifling is a big factor. If someone can tell me how to insert pictures I will upload recovered pellets. Some have realy deep engraving but no distortion and still give excellent accuracy.
    Guido is right though this discussion could tie up this whole site!

  15. #15
    Sharp Shooter
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    k well im happy for you oaks, but im not going to argue...

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