Pellets don't rise!

Discussion in 'General Airgun Chat' started by KeithW, Nov 8, 2019.

  1. Ballisticboy

    Ballisticboy Active Member

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    Below is a diagram of two identical .177 pellets, both fired horrizontally with no barrel flip etc. one having the usual zero yaw trajectory the other having just 1.5 degrees of initial yaw in the vertical direction. The tracks are just what you would see if you stood alongside the trajectory and could see the pellets flying along. The barrel is pointing along the horrizontal zero height line. The real pellet is still starting out flying horrizontally but the yaw is creating aerodynamic lift. Probably the first thing which will strike you is that the maximum height is very small which is true but it still represents some degree of pellet lift above the barrel line.

    pellet lift.jpg

    Of course many will say that is just theory and nothing like that ever happens in real life but in real life no pellet ever leaves a barrel without some yaw or yawing rate on it. Also if the modelling is so wrong please don't tell the army, or navy of just about any country as they all use it for aiming their guns and training their personnel.
     
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  2. KeithW

    KeithW Barn door? Where?

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    My point was that pellets don't rise of themselves (when fired horizontally). The debate has opened up a bit now as to whether we are angling our rifles up or our scopes down... :D
     
  3. MikeSeago

    MikeSeago Sloth like member

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    BB. What would cause the vertical yaw. Is it a result of the rifling, a flaw in the barrel or just the spin imparted on the pellet by the rifling ?
     
  4. KeithW

    KeithW Barn door? Where?

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    In that case, I certainly stand corrected. Is yaw an effect of the aerodynamics of the pellets?
     
  5. Tiger

    Tiger Member

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    Thank you Ballisticboy.

    Does that rise and drop you illustrate continue for the duration of the pellet flight? If so, does the amplitude decay with time (because the spin rate reduces as the pellet speed diminishes due to the drag)?

    Does the pellet also experience this phenomenon laterally as well as vertically? If so, are they in phase, i.e. the path is a spiral (assuming the amplitude decays) or can they be out of phase causing an irregular flight path? Can the phases be managed?
     
  6. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    That's my excuse right there for hitting high on those those pesky micro-reducers...;)
     
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  7. Wheelieneilie

    Wheelieneilie Active Member

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  8. Ballisticboy

    Ballisticboy Active Member

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    Yaw on leaving the barrel is a result of what happens in the gun. It can be caused by many things such as uneven wear on the sides of the pellet, a pellet being put into the breach slightly crooked etc. The yaw may increase after leaving the barrel due to the aerodynamics before decreasing on a stable pellet. The direction of the yaw will be random from shot to shot but some can be vertical. There are also yaw rates on leaving the gun which are more common again caused by what happens in the gun and on leaving the barrel.

    The rise and drop (known as heave and swerve on projectiles) occurs in every direction with the precession yaw cycle. As the yaw goes through its cycle so the movement of the pellet will follow. There is also a nutation cycle but it is too fast to have much effect on the trajectory. The dynamic stability of the pellet will decide if the yaw and size of the heave and swerve increase or decrease. Unfortunately pellets seem to be largely dynamically unstable, particularly at high muzzle velocities and longer ranges leading to increased movement of the pellet and some degree of spiralling.

    The physical and aerodynamic properties of the pellet will decide the cycle wave length so some degree of control is possible with careful design.
     
  9. MikeSeago

    MikeSeago Sloth like member

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    Thanks BB.
    An excellent explanation
    I think the best option for me is to forget all of this and go back to ‘pull trigger, target fall down. Yeah’
     
  10. Ballisticboy

    Ballisticboy Active Member

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    Or if you're like me , "pull trigger, target still standing, oh bug**r."
     
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  11. Nomads HFT

    Nomads HFT Well-Known Member

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    According to one of our esteemed regulars at Nomads, that's nothing to do with external ballistics; it's because the target was in the wrong place. Usually the target is an inch high, low, left or right; sometimes more.
     
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  12. Tone

    Tone Active Member

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    Maybe it is because the targets rise, not the pellets, that Ash misses the target, but his number one excuse is that the target is in the wrong place :)

    whoops did I just disclose the 'esteemed' members name :D
     
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  13. Archer50

    Archer50 Active Member

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    So let's see if I've got it right:

    Does the pellet rise with respect to the shooters line of sight? If the barrel is pointing above horizontal, yes.

    Does it rise with respect to the bore line? No, except for the small effect Ballisticboy outlined.

    Which is the correct answer? Both - it depends on the initial premise, context and purpose of the question/statement, which was not defined clearly in the first instance.

    Am I going out to shoot a few pellets with my mates before this thread, interesting though it is, becomes more about semantics than ballistics? Yes....

    Alan
     
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  14. blacklab

    blacklab Active Member

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    do we have to start wearing an earth wire because of the amplitude:eek::eek::eek::eek::eek::D
     

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