Firearm Injuries

🔫 Firearm Basics

• A firearm uses gas from an explosion to fire a projectile

• Ballistics = science of projectiles:

  • Internal: what happens inside the gun

  • External: what the bullet does in the air

  • Wound: what happens when it hits the body

• Types include: air guns, handguns, shotguns, rifles, submachine guns, modified imitation guns

🧾 How Firearms Are Classified

By barrel:

• Smooth bore: shotgun

• Rifled: pistols, rifles

• Country-made or homemade

• Air guns

• Paradox guns (half-rifled)

By speed of bullet:

• Low (<1200 ft/s): e.g. pistol

• Medium (1200–2500 ft/s)

• High (>3000 ft/s): machine guns

🛠️ Parts of a Firearm

• Barrel

• Grip/butt/stock

• Action: trigger, trigger guard, bolt, hammer

🔫 Weapon Types

Handguns:

• Use lead bullets

• Have rifled barrels

• Short-range, lower velocity (~300 m/s)

Rifles:

• Use jacketed bullets (lead inside, metal outside)

• High velocity (>1000 m/s)

Shotguns:

• Fire many small lead balls (pellets)

• Smooth barrel, sometimes narrowed at the muzzle (“choke”)

• Usually fired from 30–50 m

• Some are cut shorter by criminals to hide

💣 Ammunition Basics

• A “round” includes:

  • Bullet or shot

  • Casing

  • Propellant (powder)

  • Primer (to start the explosion)

Shotgun ammo:

• 200–350 pellets per cartridge

• Wads (cork/plastic) separate powder from pellets

💥 How a Gun Fires

1. Firing pin hits primer → sparks

2. Powder burns → hot gas forms fast

3. Bullet shoots out with smoke, flame, gas

4. Gas, soot, or powder can leak from the back end (breech)

5. Flame can be as long as the barrel

🧍 Gunshot Wound Basics

• Wound severity = how much kinetic energy hits the body

• High-speed bullets do more damage

• Damage depends on:

  • Barrel type (rifled or smooth)

  • Bullet type and speed

  • Propellant

  • Shotgun choke

  • Range and angle of fire

🔘 Shotgun Injuries

• Pellets start close together and spread with distance

• Closer range = tighter, deeper, single hole

• Longer range = wider, scattered pattern

Injury ingredients:

• Pellets

• Soot

• Burning powder

• Hot gases and carbon monoxide

• Wads and bits of cartridge

📏 Shotgun Wound by Distance

Contact (tight):

• One round hole, same size as barrel

• Soot around edge

• Muzzle mark may be visible

• Pink tissue from CO gas

• Wads found deep inside

Close range (few cm):

• Clean edge or slightly torn

• No pellet spread

• Soot, powder burns, tattooing

• Wads deep inside wound

Intermediate (~30 cm):

• "Rat hole" with rough edge

• Still no pellet holes

• Soot and tattooing

• Less CO in tissue

• Wads present

Longer range (1–5 m):

• Central hole + scattered pellet marks

• Little or no soot

• Tattooing fades with distance

• Wads not in wound but may leave marks

Beyond 5 m:

• Scattered pellet wounds

• No central hole

• No soot, no tattoo, no wad marks

🔄 Exit Wounds

• Less common in chest/abdomen

• More likely in head, arms, legs, thin adults

• Can be large and ragged

• Depends on bone, angle, tissue type

🌀 Wounds from Rifled Weapons

Entry:

• Round hole if shot straight

• Oval if shot at an angle

• Edges turned inward

• Abrasion ring and black rim

• May contain clothing fibers, soot, and carbon monoxide

Exit:

• Usually larger and irregular

• Edges turned outward

• May look small if skin is tight (e.g. against a belt)

• No soot or powder marks

💥 Special Wound Types

Over soft tissue (contact shot):

• Round hole

• Muzzle mark

• Bruising

• CO redness

• No outside soot

Over bone (contact):

• Star-shaped tear

• Peeling of outer bone layer

• Soot under skin

• No outer powder marks

Close range (<15 cm):

• Hole with edge ring

• Burnt hairs, soot, tattooing

• Powder flakes on skin

• Little or no CO in tissues

Medium range (15–60 cm):

• Ring of dirt

• No soot or burns

• Maybe powder tattooing at 15–30 cm

• No CO or hair burning beyond 30 cm

⚠️ Inside the Body

Low-velocity bullets:

• Local damage like bruising, tearing

• Organs bleed from impact

High-velocity bullets:

• Create shockwaves (cavitation)

• Damage far bigger than bullet size

🧪 Autopsy After a Gunshot Death

• Swab hands and wounds for powder

• Do X-rays to find bullets or pellets

• Collect bullets, shot, or wads as evidence

• Photograph and describe wounds exactly

🛠️ Weapons That Can Imitate Gunshots

• Air guns

• Rubber/plastic bullets

• Stud guns (used in construction)

• Captive bolt guns (used to kill animals)

• Crossbows

1. What is a Firearm?

A firearm is any device or weapon designed to propel a projectile (bullet or shot) through the explosion of gases. This gas results from the combustion of an explosive substance, usually gunpowder or nitrocellulose.

Examples of Firearms:

• Air gun: Uses compressed air to shoot pellets.
  
  

• Shotgun: Fires many small pellets (lead shots).
  
  

• Handgun: Includes pistols and revolvers.
  
  

• Submachine gun: Fires bullets rapidly using automatic mechanisms.
  
  

• Assault rifle: Military-grade rifles like the AK-47.
  
  

• Modified imitation guns: Look-alikes changed to shoot real bullets.
  
  

2. What is Ballistics?

Ballistics is the scientific study of the motion and impact of projectiles.

Types of Ballistics:

• Internal ballistics: What happens inside the gun when it’s fired.
  
  

• External ballistics: How the bullet travels through the air after it leaves the gun.
  
  

• Wound ballistics: How the projectile behaves when it enters the human body and what damage it causes.
  
  

3. Classification of Firearms

A. Based on the Barrel Type:

1. Smooth bore firearm (e.g., shotgun): Barrel has no grooves. Fires pellets.
   
   

2. Rifled firearm: Barrel has spiral grooves that make the bullet spin, increasing accuracy.
   
   

3. Country-made firearm: Crude or homemade gun.
   
   

4. Air gun: Uses compressed air instead of explosive force.
   
   

5. Paradox gun: Partly rifled barrel.
   
   

B. Based on Muzzle Velocity (speed at which bullet exits the barrel):

1. Low velocity: ≤ 1200 feet/second (e.g., revolvers).
   
   

2. Medium velocity: 1200–2500 feet/second.
   
   

3. High velocity: > 3000 feet/second (e.g., assault rifles).
   
   

4. Structure of a Firearm

• Barrel: Long tube through which bullet travels.
  
  

• Grip / Butt / Stock: Held by the shooter.
  
  

• Action (firing mechanism), includes:
  
  

  • Trigger: Starts the firing process.
    
    

  • Trigger guard: Protective loop around the trigger.
    
    

  • Bolt: Loads and seals the cartridge.
    
    

  • Striker/Hammer: Hits the firing pin to ignite the bullet.
    
    

5. Ammunition

Ammunition includes all materials used for firing:

• Bullet or pellet: The actual projectile.
  
  

• Cartridge case: Holds the bullet and propellant.
  
  

• Primer: Small explosive that starts the reaction.
  
  

• Propellant: Usually gunpowder or nitrocellulose flakes that generate gas.
  
  

6. Shotgun vs. Rifle Ammunition

• Shotgun cartridge:
  
  

  • Contains 200–350 lead pellets (2.5–3.5 mm each).
    
    

  • Has a wad (felt/cardboard/plastic) to separate powder and pellets.
    
    

  • Plastic or cardboard outer casing, with metal primer at the base.
    
    

• Rifle cartridge:
  
  

  • Fires a single bullet with high energy.
    
    

  • Bullet often made of lead, sometimes jacketed in cupronickel (a copper–nickel alloy).
    
    

7. Discharge Process (Firing a Gun)

1. Trigger pulled → firing pin strikes primer cap.
   
   

2. Primer explodes, igniting the propellant (e.g., nitrocellulose).
   
   

3. Hot gases expand and force the bullet out of the barrel.
   
   

4. Flame, smoke, unburnt powder, and gas may follow.
   
   

5. Flame length usually equals barrel length.
   
   

6. Gas leaks may occur at the breech (rear of the gun).
   
   

8. Gunshot Wounds

Wounds result from transfer of kinetic energy (KE = ½ mv²) from projectile to tissue. Velocity is the key factor—high-speed bullets do more damage.

Important Considerations:

• Type of weapon and barrel (smooth or rifled).
  
  

• Muzzle velocity.
  
  

• Type of projectile (bullet vs pellets).
  
  

• Type of propellant.
  
  

• Degree of “choke” (narrowing of barrel tip).
  
  

• Range and angle of fire.
  
  

9. Shotgun Wounds

• At short range, pellets act like a single mass → tight central wound.
  
  

• With distance, pellets spread in a cone shape → wider, scattered wounds.
  
  

• Wound size increases with distance.
  
  

Injury also caused by:

• Lead pellets
  
  

• Flame and hot gases
  
  

• Burning/unburnt gunpowder
  
  

• Carbon monoxide (causes pink tissue)
  
  

• Wads (can be found deep in wound)
  
  

• Fragments of the cartridge
  
  

10. Wound Types by Range

Contact Wound (Gun pressed against skin):

• Single round wound matching barrel size.
  
  

• Blackened edge from burning.
  
  

• Bruising and muzzle imprint.
  
  

• Wads found deep in body.
  
  

• Pink discoloration (from carbon monoxide in tissues).
  
  

Intermediate Range (few cm to 60 cm):

• Skin burns, soot, powder tattooing (small dot-like burns).
  
  

• “Rat-hole” wounds: central hole with ragged edges.
  
  

• Powder flakes in skin.
  
  

Long Range (1–5 meters):

• Central hole with satellite pellet holes.
  
  

• No soot or burns.
  
  

• Wads rarely enter the body but may leave an imprint.
  
  

Very Long Range (>5 m):

• Wide scatter of pellets.
  
  

• No central hole.
  
  

• No soot, tattooing, or burns.
  
  

11. Entry vs Exit Wounds

Entry Wound:

• Small, round if bullet hits at 90° (perpendicular).
  
  

• Oval or elliptical if bullet enters at an angle.
  
  

• Edges are inverted (bent inwards).
  
  

• May have abrasion collar: Ring of dirt or grease from bullet.
  
  

• May contain fibers or carbon monoxide staining.
  
  

Exit Wound:

• Often larger and irregular with everted (outward-turned) flaps.
  
  

• May be stellate (star-shaped).
  
  

• No soot or powder tattooing.
  
  

• If skin is supported (e.g., by a belt), it may be small.
  
  

12. Gunshot Wounds to Bone

• Bone entry: Round hole with internal chipping.
  
  

• Bone exit: Larger, more destructive due to force dispersion.
  
  

• May leave bone fragments and cause “secondary missiles.”
  
  

13. Damage to Internal Organs

Two categories:

1. Low-velocity injury:
   
   

   • Causes contusion (bruising) and laceration (tearing) by mechanical force.
     
     

   • Localized bleeding and disruption.
     
     

2. High-velocity injury:
   
   

   • Causes cavitation: Temporary cavity in tissues due to shock wave.
     
     

   • Results in greater destruction than bullet size would suggest.
     
     

14. Postmortem (Autopsy) Procedures

• Swab wound for powder residues.
  
  

• Swab hands for gunpowder or primer traces.
  
  

• X-ray to locate bullets or pellets.
  
  

• Collect and preserve:
  
  

  • Bullets, wads, pellets
    
    

  • Clothing fibers
    
    

• Document wounds carefully and take photographs.
  
  

15. Other Weapons That Mimic Firearms

• Air guns and rifles: Low-velocity; can still cause penetrating injury.
  
  

• Rubber/plastic bullets: Used for crowd control. Can cause blunt trauma.
  
  

• Stud guns: Used in construction to drive nails into walls.
  
  

• Humane killers (captive bolt pistols): Used in slaughterhouses; cause instant brain damage.
  
  

• Crossbows: Fire arrows; can penetrate deeply and may be fatal.