Slow motion 71 yards full flight

Forums General Discussion Slow motion 71 yards full flight

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    Yrrah
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    Recording full flight over longer ranges at high magnification isn’t easy; and graininess is to be expected.
    But it allows the pellet’s flight characteristics, things like precession and spiral,  to be analyzed.

    .177 JSB 8.44 gr Exact shot from RAW TM 1000 at approx 880 fps through a soup spoon (weakened by previous shots) at 71 yards.

     http://vidmg.photobucket.com/albums/v392/Kyogle/My%20Movie_zpsbgxckbjs.mp4

    Now see what happens to the same pellet if shot at 1010 fps  about Mach 0.9 nearing the speed of sound: Same 71 yd range:
    http://vidmg.photobucket.com/albums/v392/Kyogle/1010%20fps%208.44%20gr%20spiral%20flight_zpspd1x5mp4.mp4

    Note the group size compared to the two groups higher up that were shot at the same 880 fps as the spoon shot.
    Harry.

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    Dirte
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    Cool! I watched it about five times. Nice spinner also.

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    Bluestone
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    Harry, the spiraling seems to start near the muzzle; so not induced by yawing from lower linear velocity and relatively high angular velocity at long range.

    So why does the higher, but still subsonic mv, cause this spiraling and would a ST barrel help ?

     

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    Yrrah
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    Blue, the spiral actually begins at the peak/apogee of the trajectory, if you look closely.
    That is at approx 38 or 39 yards in that shot. Up to there it may well be quite accurate at that velocity; which gives rise to the often conflicting opinions/experience shooters express.

    Second part of the question. The shock wave off the head of the pellets begins at well below local speed of sound. By Mach 0.8 to 0.9 it is already attached on round head pellets and well before that on wadcutters.  That MV is then where the much higher drag begins; and the flight becomes dis-proportionally susceptible to wind deflection. In a sense the shock wave and the pellet seem to begin to act almost as one unit of apparent diameter larger than the pellet itself.

    As to the question respecting ST barrel helping –  I have not done the necessary amount of work with my ST barrels at that velocity range  to say yay or nay.
    Kind regards, Harry.

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    Bluestone
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    Harry, I have now watched the trajectory several times and I think you’re right. 

    So, why does the spiraling start at or near the apogee ? 

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    Yrrah
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    “Bluestone”Harry, I have now watched the trajectory several times and I think you’re right. 

    So, why does the spiraling start at or near the apogee ? 

    
Conjecture:
    I think, in this case,  it begins when a statically over-stabilized pellet wants to continue pointing its axis in the initial/immediate direction of travel and will not maintain tractability, ie., tip over and maintain its axis aligned to the descending trajectory. Gravity is pulling it down somewhat side on and that together with the resultant changing orientation of the Windforce sets up moments which result in precession and then spiral flight.   … I think …. Harry.

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    GQ
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    Yarrow what rifle are you shooting on those videos ?

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    chasdicapua
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    Truly, faster is not better/more accurate!

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    Yrrah
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    “GQ”Yarrow what rifle are you shooting on those videos ?

    
As indicated in the OP: “.177 JSB 8.44 gr Exact shot from RAW TM 1000 at approx 880 fps through a soup spoon (weakened by previous shots) at 71 yards”.
    It is my competition Bench Rest rifle made in Tennessee by Martin Rutterford. … Best regards, Harry.

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    Bwalton
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    Thanks for posting that,  that’s exactly what I have to explain time and time again, pellets have a max stable velocity. Most ppl that I tune rifles for wants high velocity which I tell them that they are going to loose accuracy. One prime example is when I went out pesting the very last time due to the heat and the higher elevation the gun start shooting very fast opposing where it was tuned at sea level in a fair amount of humidity along the coast. 930fps is the max that I can shoot without having some stability loss in .25cal and up. So I tune the rifles at 915-920 to leave room for thin air and heat. Again this depends on barrel length as well. a barrel thats 23inch I can go 930fps, a barrel thats19inches I go around 880-890fps, if im going to traveling away from the coast then I would go 870fps to allow for velocity change,

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