Barrel length

Discussion in 'Piston & Spring' started by Andy B, Oct 11, 2018.

  1. NeilM

    NeilM Well-Known Member

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    The handling is certainly different due to the shorter barrel and lever on the HC and as far as I know the stoke and pistons on the two rifles are identical so maybe my logic is flawed, but the HC is a fair bit harder to cock than the full rifle.
     
  2. Andy B

    Andy B New Member

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    Having had both models side by side, which do you prefer?
     
  3. Andy B

    Andy B New Member

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    Marginal gains in accuracy may well be lost on me!
     
  4. NeilM

    NeilM Well-Known Member

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    Not decided yet, I've only had them a week.

    The full rifle definitely more nose heavy and is much easier to cock and the HC feels chunky until you get it into the shoulder then the neutral balance make it very easy to handle. I'll be out on an FT course with them as soon as the weather allows..... 50 MPH winds down here at present.
     
  5. Andy B

    Andy B New Member

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    Pretty special in Cornwall at the moment too. I thought things were improving but just looked at the forecast :(
     
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  6. Adam

    Adam Active Member

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    The difference is tiny, and outweighed by the additional mass of the barrel and cocking lever damping muzzle movement.
     
  7. Nomads HFT

    Nomads HFT Active Member

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    The full barrel takes in the region of 0.3 milliseconds longer than the HC for 7.87gn pellets at circa 805fps.
     
    Last edited: Oct 12, 2018
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  8. JoostB

    JoostB Member

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    Hmm that is not much
     
  9. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    Another 20-30mph might even persuade ol’ Jon to get out on a course with a rifle for some old Skool FT....
     
  10. Nomads HFT

    Nomads HFT Active Member

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    Having owned both the TX200 and HC, I much prefer the full rifle, and found it slightly easier to achieve any given standard of accuracy with, partly due to the extra mass of the longer barrel reducing muzzle lift, but mainly due to the higher energy efficiency of the longer barrel, which means that the HC has to be pushed that bit more to achieve equivalent muzzle velocity - the piston has to travel slightly faster and further, reflected in the recoil.

    TX & HC recoil.jpg

    Air Arms Express 7.87gn pellets, 808fps (HC) and 809fps (TX).
     
    Last edited: Oct 14, 2018
  11. Andy B

    Andy B New Member

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    I'd agree with the mass and length helping to regulate muzzle flip. Along the lines of my thoughts

    Interesting graph. How was it generated/measured?
     
  12. hmangphilly

    hmangphilly The Doctor

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    Interesting to measure recoil in mm
     
  13. Nomads HFT

    Nomads HFT Active Member

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    Linear generator and/or 400g accelerometer feeding a USB digital recording oscilloscope gives recoil velocity/acceleration respectively, integrated to find displacement.
     
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  14. Nomads HFT

    Nomads HFT Active Member

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    It's easy to calculate to give you a good idea of what primary recoil will be, Phil. Available piston stroke minus a mm to guesstimate the compression stroke, multiplied by the weight of the piston plus a third the weight of the spring, divided by all up rifle/scope weight.

    For my 85mm TX, that's 84 (mm) divided by 0.251 (Kg) multiplied by 4.6 (Kg), or 4.58mm. In my test rig, I record around 4.5mm, the difference being the tiny amount of friction between the rifle and rig.
     
  15. RobF

    RobF Administrator Staff Member

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    Does that mean though that a piston with a hole in it will recoil the same as a piston without?
     
  16. Nomads HFT

    Nomads HFT Active Member

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    I don't quite follow you, Rob. Do you mean a piston with a hole in the face so it doesn't compress air? If so, the primary recoil displacement will be slightly greater as the piston travel would be greater. In all other respects, the recoil cycle would differ hugely.
     
  17. RobF

    RobF Administrator Staff Member

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    That's what I'm getting at... surely the recoil distance cannot depend upon just the stroke divided by spring weight x the gun weight...?
     
  18. Nomads HFT

    Nomads HFT Active Member

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    It's a ball park figure, Rob, but yes, primary recoil displacement is dependent on the length of the compression stroke (itself affected by pellet start pressure and mass, spring and preload, transfer port length and diameter, and hence a guesstimate) multiplied by the mass of the piston plus a third the mass of the spring, divided by the combined rifle/scope mass.
     
  19. Adam

    Adam Active Member

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    I was wondering where spring rate was in the equation but I guess that primarily affects recoil acceleration rather than overall displacement. Hence how "soft" or "snappy" it feels?
     
  20. Nomads HFT

    Nomads HFT Active Member

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    Exactly, Adam.

    Spring rate and preload affect the nature of the recoil cycle, and any effect on primary recoil displacement can only come if they alter the piston displacement.
     

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