Notes · Forensic Medicine · 26 October 2026

Firearm Injuries – Ballistics

Definition

• Firearm injury: tissue damage caused by the discharge of a weapon that uses the rapid expansion of gases to propel a projectile (bullet) at high velocity.
• Ballistics: the scientific study of the behavior of a projectile from the moment of ignition in the firearm to its interaction with the target, divided into internal, external, and terminal ballistics.

Epidemiology

• Firearm‑related deaths account for ~15 % of all injury deaths worldwide; the burden is highest in the Americas, parts of Africa, and conflict zones.
• In India, accidental firearm injuries are rare (<0.1 % of all trauma) but homicide and suicide with firearms are increasing, especially in urban areas.
• Male predominance (≈ 85 %) and the age group 15‑35 years are consistently reported.

Aetiology (Types of Firearms & Ammunition)

• Handguns (pistols, revolvers): short barrel, low to moderate muzzle velocity (≈ 250‑350 m/s).
• Rifles (bolt‑action, assault): long barrel, high muzzle velocity (≈ 600‑900 m/s).
• Shotguns: fire multiple small pellets (buckshot) or a single slug; muzzle velocity ≈ 400‑500 m/s.
• Ammunition:
  • Full‑metal‑jacket (FMJ) – bullet core covered by a metal jacket; tends to retain shape and penetrate deeply.
  • Hollow‑point (HP) – cavity at tip expands on impact, increasing tissue damage but reducing over‑penetration.
  • Soft‑point (SP) – partially exposed lead tip, intermediate behavior.

Ballistics

Internal Ballistics (inside the firearm)

• Ignition: primer ignites propellant powder, generating high‑pressure gas.
• Pressure curve: peak pressure (≈ 30‑50 MPa for rifles) is reached within milliseconds; pressure then falls as the bullet travels down the barrel.
• Muzzle velocity (V₀): speed of the bullet as it exits the barrel; calculated by V₀ = √(2 × Work/ mass).

External Ballistics (flight through air)

• Trajectory: bullet follows a parabolic path affected by gravity, air resistance, and wind.
• Ballistic coefficient (BC): a measure of a bullet’s ability to overcome air resistance; higher BC = flatter trajectory.
• Supersonic vs. subsonic: bullets > 340 m/s are supersonic, producing a “sonic crack” that can cause additional tissue damage.

Terminal Ballistics (interaction with target)

• Permanent cavity: tissue physically displaced or destroyed by the bullet’s path; size depends on kinetic energy (KE = ½ mass × velocity²).
• Temporary cavity: rapid radial stretch of tissues caused by the shock wave; more pronounced in elastic tissues (muscle, liver) than in inelastic tissues (bone, brain).
• Yaw, tumble, fragmentation: loss of bullet stability can increase cavitation and produce irregular wound tracks.

Pathophysiology

• Direct crush injury: immediate destruction of cells along the bullet track.
• Stretch injury: temporary cavity creates shear forces, leading to vascular rupture, nerve stretch, and organ laceration.
• Ballistic pressure wave: high‑frequency pressure transmitted through the body can cause remote organ injury (e.g., brain concussion from a peripheral wound).
• Secondary projectiles: bone fragments or bullet fragments can act as additional missiles, enlarging the wound.

Clinical Features

Investigations

• Primary survey (ATLS): airway, breathing, circulation, disability, exposure – immediate life‑saving measures.
• Imaging:
  • Plain radiograph: locate metallic projectiles, assess bone injury.
  • Focused Assessment with Sonography for Trauma (FAST): detect pericardial or intra‑abdominal fluid.
  • CT angiography: delineates vascular injury, especially in neck, torso, and extremities.
• Forensic sampling:
  • GSR swabs from wound margins and clothing (microscopic analysis).
  • Bullet recovery: caliber, rifling marks, and deformation examined to match firearm.
  • Chain of custody documentation for all evidence.

Management (Current Guidelines – ATLS 2024 & WHO 2023)

1. Immediate resuscitation – control hemorrhage with direct pressure, tourniquets, or pelvic binders; initiate massive transfusion protocol if > 1 L blood loss.
2. Airway protection – early intubation for facial or cervical injuries; consider surgical airway if airway compromised.
3. Breathing – chest tube insertion for pneumothorax/hemothorax; ventilatory support as needed.
4. Circulation – permissive hypotension (SBP ≥ 90 mmHg) until surgical control of bleeding; balanced blood product ratio 1:1:1 (PRBC:FFP:Platelets).
5. Definitive hemorrhage control – damage‑control surgery (DCS) for exsanguinating torso injuries; prioritize vascular repair, organ packing, and temporary abdominal closure.
6. Antibiotic prophylaxis – broad‑spectrum coverage (e.g., cefazolin + metronidazole) for penetrating torso wounds; extend based on contamination.
7. Tetanus prophylaxis – tetanus toxoid booster if > 5 years since last dose, or tetanus immune globulin if wound is heavily contaminated.
8. Pain and sedation – multimodal analgesia; consider ketamine for hemodynamically unstable patients.
9. Psychological care – early counseling for survivors; mandatory reporting to law enforcement per local statutes.

Complications

• Hemorrhagic shock – leading cause of early mortality; uncontrolled arterial or venous bleeding.
• Infection – retained bullet fragments, devitalized tissue, and foreign material increase risk of abscess and osteomyelitis.
• Neurovascular deficit – permanent loss of limb function or spinal cord injury.
• Fat embolism – especially after long‑bone fractures from high‑energy bullets.
• Lead poisoning – chronic exposure from retained lead bullets, particularly in intra‑articular or intraventricular locations.
• Psychiatric sequelae – PTSD, depression, and suicidal ideation are common in survivors.

High‑Yield Exam Points

• Three phases of ballistics – internal, external, terminal; know the key parameters (pressure, muzzle velocity, kinetic energy).
• Stippling vs. tattooing – stippling = powder particles (≤ 2 m), tattooing = soot (≤ 30 cm).
• Muzzle imprint – indicates contact shot; may show soot, burned skin, and a circular abrasion.
• Kinetic energy formula – KE = ½ × mass × velocity²; small increase in velocity dramatically raises energy.
• Temporary vs. permanent cavity – temporary cavity causes stretch injury; permanent cavity is the actual tissue loss.
• Management priority – “C‑ABC” in massive hemorrhage: catastrophic hemorrhage first, then airway, breathing, circulation.
• Damage‑control surgery – abbreviated operation to stop bleeding and contamination, followed by ICU resuscitation and definitive repair later.
• Forensic evidence – GSR, bullet caliber, rifling marks, and wound characteristics help link weapon to injury.

Practice questions

1. A 28‑year‑old male is brought to the ED with a single entry wound on the anterior abdomen and no obvious exit wound. The wound shows a central puncture with an abrasion ring and fine black particles around it. Which of the following best explains the black particles?
   Answer: B — they represent soot tattooing, indicating a contact or near‑contact shot.

2. Which ballistic parameter most directly determines the size of the permanent cavity produced by a bullet?
   Answer: C — kinetic energy (½ mass × velocity²).

3. According to the 2024 ATLS guidelines, the first step in managing a patient with a massive penetrating torso injury and uncontrolled hemorrhage is:
   Answer: A — control catastrophic hemorrhage (C‑ABC approach).

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AI-assisted study material for exam revision. Always confirm with standard textbooks and current guidelines; not medical advice.