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bullet tumble and drag

Mr. PerfectMr. Perfect Member, Moderator Posts: 63,779 ******
edited November 2013 in General Discussion


Some interesting and highly mistaken comments on this video as to why the "sabots" are not stabilizing. I'd appreciate you-alls input, but my understanding is that you either need to impart a large rotational spin rate or you need to balance the center or mass forward of the geometric center to avoid tumble, and preferably both. Objects simply don't fly light end forward very long.
Some will die in hot pursuit
And fiery auto crashes
Some will die in hot pursuit
While sifting through my ashes
Some will fall in love with life
And drink it from a fountain
That is pouring like an avalanche
Coming down the mountain

Comments

  • Mr. PerfectMr. Perfect Member, Moderator Posts: 63,779 ******
    edited November -1
    quote:Originally posted by forgemonkey
    quote:Originally posted by Mr. Perfect


    Some interesting and highly mistaken comments on this video as to why the "sabots" are not stabilizing. I'd appreciate you-alls input, but my understanding is that you either need to impart a large rotational spin rate or you need to balance the center or mass forward of the geometric center to avoid tumble, and preferably both. Objects simply don't fly light end forward very long.



    ,,,,you obviously haven't seen me on a trampoline !!!!![:D][;)]
    If you think that's yer light end...
    Some will die in hot pursuit
    And fiery auto crashes
    Some will die in hot pursuit
    While sifting through my ashes
    Some will fall in love with life
    And drink it from a fountain
    That is pouring like an avalanche
    Coming down the mountain
  • machine gun moranmachine gun moran Member Posts: 5,198
    edited November -1
    A projectile can be stabilized by spin, fin, or balance, or a combination.

    The British .303 MkVII was designed as a nose-light projectile which would stay nose-on in the air from its gyroscopic spin, but the superior forces which came into play when striking a soft target (greater projectile inertia in the base than in the nose) would cause the base to try to fight its way past the nose. It always succeeded, because yaw is always present to some degree and no bullet ever strikes exactly point-on (there is no such thing as a perfect bullet).

    Even if a bullet were to strike perfectly point-on, unequal resistance on one side of the bullet (oblique hits, inconsistent tissue density) would throw the light nose off-axis and the heavier base would start to take the lead. Long story short, The MkVII was a fiercer killer than many softnose bullets. The point fillers were originally kapok, then aluminum, and ultimately many other lightweight materials. When the Chinese copied the design into their ammunition, they used tiny plastic beads as a point filler. I believe the Yugo 7.62x39 M67 uses just an air void. This bullet changes ends in soft tissue in about 3 inches of penetration, as opposed to a foot for solid fmj's.

    I've read things like 'The M67 bullets work by the forward movement of the core in the jacket when the bullet meets resistance, destabilizing the bullet', but this is nutzo. Movement of the core into the nose would have the opposite effect, tending to stabilize the bullet by moving mass forward on the axis, and lightening the base.

    There is no magic in stabilization, or in de-stabilization.
  • A J ChristA J Christ Member Posts: 7,534
    edited November -1
    Got to do with the rte of spin.

    The early 5.56 had a 1:14 rate with 55grain rounds and it kinda, sorta stabilized bullets, usually. They changed the rate to 1:12 and that fixed it. Until they went to a heavier bullet, then they went to 1:9 to stabilize them.

    A few years back one of the ammo companies, Remington I think, sold 30-30 with a 22 caliber sabot bullet. Great idea but the rate of spin was too slow to adequately stabilize those bullets.

    As long as the bullet travels as intended, all is good, when they slip and go sideways or tumble, they don't do so well anymore.
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