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Thread: Longer barrel on pcp

  1. #1
    Sharp Shooter

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    Default Longer barrel on pcp

    What will happen if a longer barrel is fitted to a pcp without tuning or modifying the rifle.

    -What will happen to the velocity?
    -Will the accuracy improve especially on longer shots?

    I know Boondock Fitted a 26" barrel to his Condor.

    Ive been told to expect a 15 fps gain per longer inch. Is this true?
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  2. #2
    Sharp Shooter

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    All equil accuracy won't change because of barrel length, velocity will go up
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  3. #3
    Sharp Shooter

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    A longer barrel will invariably increase power. The level of power increase will depend on the pellet used and tuning, I.E. what you want to get out of it. It will not necessarily improve accuracy.
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  4. #4
    Sharp Shooter

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    BTW: 26" is too long to carry around comfortably. I would not go over 24".
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  5. #5
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    Might as well poke the pigeon in the eye!
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  6. #6
    Sharp Shooter

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    Spyker, Thanks for the K@K advise........lol
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  7. #7
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    Any reasons why a longer (unchoked) barrel not give a velocity gain when only the barrels were exchanged and everything else is same and in order?
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  8. #8
    Sharp Shooter

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    Like we said, a longer barrel will increase power...
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  9. #9
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    A longer barrel will only increase velocity up to a certain point then friction will take its toll ...a 2 meter airgun barrel wont make your s410 shoot 2000fps...
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  10. #10
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    but where this optimum level is i dont know...i guees it will depend on the power you shoot....
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  11. #11
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    Ian DONT send my rifle back with a 26" inch barrel.Leave that experament for another time.
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  12. #12
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    Ian is converting my s410 fac to .20 for me.Looking forward to getting it back and trying it out,will do a post once I have it and tell you guys what I think.I use it for hunting and as a .177 it was great but I think in .20 it will be fantastic.
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  13. #13
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    Quote Originally Posted by spyker View Post
    Might as well poke the pigeon in the eye!

    HAHAHAHAH "Come on birdie. Come sniff here."
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  14. #14
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    Default Speed of sound

    Hmmmm..... how scientific shall we go with this one?

    Obviously it's all relative.......

    The speed of sound depends on mainly temperature for us earthlings shooting in what we call "atmosphere". Considering that sound travels at approximately 343m/s in dry air at 20C, you should take care not to exceed that at any stage during the firing cycle. If you do, the ultasonic pulse created by the air will throw your pellet off balance and your shots will be all over the place.

    Now I'm not a fundi on pcp's but know a little bit about air and ultrasonic pulse valves etc.

    My logic tells me that for a pcp, compressed air is used to accelerate the pellet in the barrel of the rifle. This means that the pellet has a certain force behind it (compressed air at whatever pressure) and that force will act on it whilst in the barrel. So, F=ma (newton's 2nd law) or a=F/m i.e. acceleration = Force / mass and then (remembering from school days) v=u+2as, (u - initial velocity obviously 0, and a = acceleration and s = distance) If we assume that u = 0m/s the formula becomes v=√(2.(F/m).s) (P.S. note that I have taken just the positive result of the formulae).

    Next, 1 Pascal is defined as 1 Newton / m. The cross sectional area of a 4.5mm Pellet = pi.r = 15.904mm or 0.000015904m. Ok, now we know the pressure of the cylinder so we should be able to calculate the force acting on the pellet from the definition of a Pascal. Let's say the cyclinder is at 300kPa - that is 300 000 Pascals or 300 000 Newton/m. So the Force = Pressure x Area - that is 300,000Pa x 0.000015904m = 4.77N (Newton)

    If we now go back to v=√(2.(F/m).s) and assume the pellet weighs 8 grain (that is roughly 0.00051839130kg) the values can be substituted into the formula and calculated for different barrel lengths.

    For a barrel length of 0.660m (26") v = 110.2m/s
    For a barrel length of 0.610m (24") v = 105.9m/s
    For a barrel length of 0.381m (15") v = 83.7m/s
    and just for fun:
    For a barrel length of 2.54m (100") v = 216.2m/s

    The same calcs but pressure increase to 400kPa: Force = 6.36Newton

    For a barrel length of 0.660m (26") v = 127.3m/s
    For a barrel length of 0.610m (24") v = 122.4m/s
    For a barrel length of 0.381m (15") v = 96.7m/s

    Having said ALL of that, reality is also that the trigger mechanism controls the time that compressed air is pushed behind the pellet i.e. for a millisecond or so, air is released from the cylinder to the rifle's barrel to accelerate the pellet. If the time is set significantly more than the time it takes the pellet to leave the barrel, air is wasted, and obviously if it is set to less, the pellet will not be accelerated through the entire length of the barrel - that means for each barrel length and pressure there will be a "sweet spot setting" for the time it releases air - please don't ask me to calculate that as well - it depends on a number of variables unique to the type of mechanism used...... I suppose trial and error and chrony will determine that best.

    In summary, increasing barrel length will increase velocity if the timer on the compressed air is sufficiently long - otherwise it will cause the pellet to go slower in fact. Hope this helps....
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  15. #15
    Sharp Shooter

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    HUUGGH???
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