Please enable JavaScript.

Coggle requires JavaScript to display documents.

Gunshot Wounds (Bullet wounds (Ballistics (Categorised (External…

- - - - Internal ballistics
        
        "the study of the propulsion of a projectile within a weapon, from the ignition of propellant until the egress of the projectile from the weapon"
        
        Determinants
        
        Propellant
        
        Chamber characteristics
        
        Barrel characteristics
        
        Rifling (imparts spin, stabilising flight)
        
        Length
      - External ballistics
        
        "the study of the trajectory of a projectile in flight"
        
        Determinants
        
        Intrinsic factors
        
        weapon size and type
        
        Bullet size and type
        
        Extrinsic factors
        
        Wind
        
        Gravity
        
        Gravity causes "bullet drop"
        
        Bullets travel in a parabolic arc
        
        Bullet drag (friction)
        
        Determines the amount of energy transferred to the target
      - Terminal ballistics
        
        "the study of the effects of a projectile on a target"
        
        Determinants
        
        Type of weapon
        
        Type of bullet (determines bullet drag, yaw, pitch and roll)
        
        Size
        
        Shape: cross-sectional diameter
        
        Material, density
        
        Tissue hit
        
        The ballistic coefficient is the efficiency of a bullet in delivering potential energy through the air to its target
    - - Effect
      - Flight
      - Behaviour
    - - The major determinant of tissue injury is bullet velocity at the moment of impact
        
        Guns are classified by their bullet velocity
        
        Medium velocity: 400-800m/s
        
        Low velocity: 400m/s
        
        e.g. handguns
        
        High velocity >800m/s
        
        e.g. rifles
        
        Air friction slows bullets down
        
        Kinetic energy decreases over distance at a logarithmic rate
        
        (The effect of friction far outweighs the effect of gravity in bullets fired downwards)
  - - - Mass
      - Velocity
        
        Bullets with sufficient energy have a cavitation effect
        
        Primary cavity: the crushed/lacerated bullet track
        
        Secondary (temporary) cavity: formed by the pressure wave from high-velocity bullets, varies depending on the tissue elasticity and tensile strength
      - Characteristics
        
        Lacerations are dependent on whether the bullet fragments (e.g. hollow tip bullets)
    - - Tissue with low elasticity are more damaged
      - Skin gut and lung: high elasticity, absorb energy - resistant to cavitation injury.
      - Fluid-filled organs (heart, bladder, blood vessels) are incompressible and therefore may burst
      - Liver, spleen and brain have poor tensile strength and so are shattered by temporary (secondary) cavitation
    - - High energy bullets become unstable as they decelerate, which may stretch tissues and tear them
      - Low-energy (handgun) bullets normally take a straight path, with one turn if they hit bone
- - - - Casing
      - Primer: ignites the propellant when hit with firing pin
      - Propellant (smokeless gunpowder)
        
        Amount of propellant varies between types of round
        
        More propellant = more muzzle velocity = more kinetic energy
      - Projectile (bullet)
        
        Material
        
        Shape
        
        Determines how bullet behaves in flight (drag)
        
        Determines penetration capability
        
        Hollow points. Used in handguns (short range) therefore flight characteristics less important. Deform readily, so bullet doesn't traverse target into a bystander, and delivers maximal kinetic energy to the target
        
        Jacket
        
        Fully jacketed bullets retain their shape in the body
        
        Partially jacketed bullets expand in the body and deliver more energy to tissue
        
        Jacket: prevents the bullet deforming in the barrel, essential if >700m/s
- - - - Revolver
        
        Revolving cylinder with muliple chambers - can fire multiple rounds
        
        Types
        
        Single action: requires the hammer to be manually pulled back before the trigger is pulled
        
        Double action: pulling the trigger (long pull) both cocks the hammer and pulls the trigger
        
        Advantages: simple, reliable, few moving parts
        
        Disadvantage: limited to 5-6 shots
      - Semi-automatic
        
        Single fixed firing chamber; magazine holding 7-17 rounds
        
        First round is chambered by manually pulling back the slide. Subsequent rounds are chambered by the egressing bullet pushing the slide backwards
      - Automatic
      - Bolt action
        
        After each shot a bolt is raised to chamber the next round (either manually or from a magazine)
        
        Most hunting rifles and sniper rifles
    - - Long arms (>10 inch barrel)
        
        Rifle
        
        Definition: long arm with helical grooves in barrel
        
        May be single shot, bolt action or automatic.
        
        Bolt action: sniper and hunting rifles
        
        Semi-automatic: assault rifles
        
        Use the recoil of the previous round to chamber the next round - can be fired repeatedly by pulling the trigger until the magazine is empty
        
        Burst fire: 3 consecutive shots (recoil normally means the subsequent shots are inaccurate)
        
        Automatic: machine guns and submachine guns
        
        Will shoot continuously as long as the trigger is pulled
        
        Submachine gun: automatic magazine-fed weapon which shoots handgun rounds
        
        Shotgun
        
        Definition: smooth bore long arm
        
        Projectiles
        
        Smallest sperical: birdshot
        
        Large spherical: buckshot
        
        00 buckshot contains 9 pellets, each with the wounding potential of one handgun round
        
        Solid lead: slugs
        
        Loading mechanisms
        
        Breach load
        
        Pump: rounds ejected and new round chambered with a pump mechanism
        
        Lever action: similar to pump, but with a lever
        
        Semiautomatic
        
        Gauge = Calibre (high gauge = low calibre)
        
        Tissue injury is determined by kinetic energy and distance
        
        Birdshot
        
        Energy of pellets reduces dramatically over distance: >50% loss over 50m
        
        At 3-7m the pellets spread and don't act as single projectile - spread will be approx 30cm and fascial penetration is common
        
        At >7m shotgun injuries with birdshot will present with many skin wounds over a large area, which do not penetrate fascia
        
        At <3m the pellets act as a single large projectile - devastating
        
        Buckshot
        
        Patients should be thought of as having received multiple handgun wounds
        
        Visceral injuries are common
        
        Conservative management is ill-advised