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Thread: Wound ballistics

  1. #21
    Let me try to define the two phenomena of sonic wave versus temporary cavity. In an article entitled

    Gunshot Wounds: 1. Bullets, Ballistics, and Mechanisms of Injury
    Jeremy J. Hollerman,1 Martin L. Fackler,2 Douglas M. CoIdwelI,3 and Yoram Ben-Menachem4

    the authors, pointd out that bullets wound tissues in two ways:
    Two major mechanisms of wounding occur: the crushing
    of the tissue struck by the projectile (forming the permanent
    cavity), and the radial stretching of the projectile path walls
    (forming a temporary cavity) (Fig. 1).
    In addition, a sonic pressure wave precedes the projectile
    through tissue. The sonic pressure wave plays no part in
    wounding. In air, the speed of sound is approximately 300 m/
    sec; in soft tissue, it is approximately 1 500 rn/sec. When a
    bullet enters soft tissue, the sonic pressure wave forms a
    hemispherical arc ahead of the advancing bullet. The shortlived
    sonic pressure pulse created may reach pressures of up
    to 100 atm (1.01 x 1 Oı Pa). The duration of this pulse is
    approximately 2 ısec [4]. Research reported in 1947 [5]
    determined that this sonic shock wave has no damaging
    effect on tissue, a finding since confirmed by clinical experience
    with sonic pressure wave lithotripsy, in which tissue
    receives sonic pressure waves two to three times greater
    than that produced by a supersonic rifle bullet [6]. The sonic
    pressure wave must not be confused with the temporary
    cavity, which is discussed later.
    There is a great deal of misunderstanding of the term sonic wave. It does not contribute to the wounding. Yet, you see this over and over again in many articles. Here is another article from the Journal of Trauma,
    http://www.neurosurgery.org/sections...ethodology.pdf -
    INFLUENCE OF BALLISTICS ON PBI
    Ballistics is the study of the dynamics of projectiles;
    wound ballistics is the study of the projectile’s action in
    tissue. Penetrating head wounds generally result from bullets,
    shrapnel, and lower velocity sharp objects, such as arrows
    and knives. The ability to penetrate the intracranial space is
    determined by the energy and shape of the object, the angle
    of approach, and the characteristics of intervening tissues
    (skull, muscle, mucosa, etc.). The primary injury to the brain
    is related to the ballistic properties (kinetic energy, mass,
    velocity, shape, etc.) of the projectile and any secondary
    projectiles, such as bone or metallic fragments.
    Lower velocity sharp projectiles, such as arrows (120–
    250 ft/s [36–76 m/s]), wooden sticks, knives, and pencils
    create a track of primary tissue damage without substantial
    bruising or blunt tearing of surrounding tissue. In contrast,
    higher velocity projectiles result in a more complex wounding
    pattern. An impact shock wave precedes the projectile.
    This sonic wave is very brief (2 s) and does not contributee
    substantially to tissue destruction. As the projectile penetrates
    brain tissue, it crushes tissue in its path, creating a permanent
    track of tissue injury. Higher velocity projectiles will impart
    an additional temporary cavitation effect in their wake, which
    is a velocity-related phenomenon. This results from the transmission
    of the kinetic energy of the projectile to the surrounding
    tissue, thus rapidly compressing it tangentially from the
    primary track. After the cavity expands to its maximum size,
    it starts to collapse under negative pressure and can suck in
    external debris. This cavity will then often undergo smaller
    expansions and contractions of diminishing amplitude. In
    relatively inelastic tissue, such as the brain, this results in a
    track of injury often 10 to 20 times the size of the offending
    projectile.

    The size of this temporary cavity is related to the velocity,
    mass, and shape of the projectile. The velocity and mass
    are proportional to the kinetic energy as defined by the
    equation KE  1/2 mv2. The shape of the projectile influences
    its velocity. Every projectile has a ballistic coefficient
    that expresses its ability to overcome air resistance and thus
    maintain velocity. A form factor in the equation for the
    ballistic coefficient relates to the shape. The sharper the nose
    of a bullet, the less the velocity will be decreased by air
    resistance. The rounder the nose of a bullet or more irregular
    the shape (as in shrapnel), the quicker the velocity slows and
    kinetic energy decreases. Projectiles traveling at higher velocities
    carry more kinetic energy and will create larger temporary
    cavities.

    The shape of the projectile also affects the size of the
    temporary cavity through its influence on yaw. Yaw describes
    the rotation of a projectile around its long axis. Although
    small amounts of circular motion (precession and
    nutation) occur during flight, projectiles will often tumble
    when striking tissue. As the projectile rotates 90 degrees to its
    long axis, the primary track of tissue destruction increases.
    The entire length of a projectile contributes to this permanent
    track when the yaw is maximized at 90 degrees. This imparts
    more kinetic energy to the tissue, and the size of the temporary
    cavity increases. This also explains why the exit wound
    is generally larger than the entrance wound in perforating
    injuries. For these reasons, a .45 automatic pistol (muzzle
    velocity of 869 ft/s [265 m/s] and a short round-nosed projectile
    with little yaw) will create a very small temporary
    cavity. Conversely, a 7.62-mm rifle (muzzle velocity 2,830
    ft/s [863 m/s] and a long, sharp nose with maximum yaw)
    will create a very large temporary cavity.

    The caliber of a weapon is defined as the internal diameter
    of the barrel and thus represents the widest diameter of
    the bullet. This may be expressed in millimeters, as in a 9-mm
    handgun, or in inches, as in a .44 magnum. Magnum refers to
    a load with extra powder, thereby imparting more velocity to
    the projectile. In general, handguns (710–1,610 ft/s [216–
    491 m/s]) will be lower velocity weapons than rifles (2,690–
    3,150 ft/s [820–960 m/s]). The velocity also will be degraded
    over distance secondary to the ballistic coefficient discussed
    above. For example, the U.S. military M16A1 rifle has a
    muzzle velocity of 3,150 ft/s (960 m/s), which drops to 2,186
    ft/s (666 m/s) at 300 yards (274 m) and 835 ft/s (255 m/s) at
    1,000 yards (914 m).

    One projectile characteristic deserving mention is fragmentation
    potential. In addition to yaw, projectiles can also
    deform or fragment on striking tissue. Copper jacketing of
    lead bullets, as mandated for military rounds by The Hague
    Peace Conference (1899), helps limit the fragmentation potential.
    Irregularities made by scoring the surface of the bullet
    (dum-dums) lead to increased fragmentation. Fragmenting
    rounds can create multiple injury tracks, as each fragment
    becomes an irregular, tumbling projectile. The Glaser round
    is filled with small pellets that disperse on impact. Hollow
    point rounds, often seen in civilian shootings, expand their
    diameter on impact, thus creating a larger primary wound
    track and more destructive temporary cavitation effects. Explosive
    bullets are designed to detonate on impact and will
    thus produce extensive tissue injury with additional kinetic
    energy transfer.

  2. #22
    Senior Member stlyin moe's Avatar
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    Funny, being around firearms all my life I've heard about "Explosive bullets" but I've NEVER seen one nor known anyone that has either. How do you keep something that is supposed to explode when contacting soft skin from not exploding under the forces of excelleration from firing?.....I sure as hell wouldn't want to shoot one.
    "Timid men prefer the calm of despotism to the tempestuous sea of liberty." ~ Thomas Jefferson

  3. #23
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    Ok, in my head I had pictured a "sonic wave" as a fast moving wave of flesh caused from the pressure of the bullet hitting and passing through it.

    I'm not sure what you would call this wave of flesh that's caused from the bullet passing through. But it can sure cause a lot of damage.

  4. #24
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    Quote Originally Posted by NorthQuad
    Ok, in my head I had pictured a "sonic wave" as a fast moving wave of flesh caused from the pressure of the bullet hitting and passing through it.

    I'm not sure what you would call this wave of flesh that's caused from the bullet passing through. But it can sure cause a lot of damage.
    Maybe that's why I have nightmares about waves of flesh coming to get me. Someone make them stop, please make them stop.
    "The world will not perish for want of wonders but for want of wonder."
    J.B.S.Haldane

  5. #25
    Quote Originally Posted by Juke_spin
    Maybe that's why I have nightmares about waves of flesh coming to get me. Someone make them stop, please make them stop.
    A flesh tsunami? . Oy.

    Wise.

  6. #26
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    Quote Originally Posted by Wise Young
    A flesh tsunami? . Oy.

    Wise.
    LOL. That would work.

    It took me a while to figure out what was meant by "sonic wave" yesterday. Sonic wave as in the wave caused by an object breaking the sound barrier type of wave. NOT a fast ripple of flesh caused by an object passing through the body at high velocity. Which is what I had emagined it meant.

  7. #27
    Quote Originally Posted by Wise Young
    A flesh tsunami? . Oy.

    Wise.
    Human Flesh Tsunami


    .

  8. #28
    Excellent source of information on ammunition
    http://thedisease.net/?ejaculate=lib...son=Ammunition

  9. #29
    Senior Member feisty's Avatar
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    this thread delivers.

    and yes, I'm talking about the prairie dog video.
    An administrator made me remove my signature.

  10. #30

    sonic wave from a supersonic bullet


    lemon being shot

    http://www.rit.edu/~andpph/exhibit-7.html

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