FM6.1-2,FM7.1-2,FM14.11 | Firearm, Blast & Regional Injuries — Practice Quiz

Rifled firearms have helical grooves (rifling) cut into the barrel's bore, imparting spin to the bullet for greater accuracy and range. Shotguns have smooth bores.

Rifling produces characteristic striations on bullets — key for ballistic identification. Smooth-bore shotguns scatter pellets and do not impart spin.

Rifling refers to spiral grooves inside the barrel that stabilise the bullet by spin. Smooth-bore firearms (shotguns) fire pellets without spin.

Calibre is the internal bore diameter — e.g., .32 calibre = 32/100 inch, 9 mm = 9 mm. It is a key descriptor for firearm identification.

Calibre (bore diameter) and gauge (for shotguns — based on the number of lead balls of barrel diameter that weigh one pound) are the two systems used to classify firearms.

Calibre refers to bore diameter, not bullet weight, barrel length, or magazine capacity.

Entry wounds are smaller, punched-out, and bear an abrasion collar (from bullet rotation/friction). Exit wounds are larger and irregular with no abrasion collar — classic through-and-through appearance.

Entry: smaller, round/oval, punched-out, abrasion collar (grease collar), inverted margins. Exit: larger, irregular, everted margins, no abrasion collar. At contact range, muzzle mark, tattooing, or stellate tears may be present.

The entry-smaller/exit-larger pattern with abrasion collar at entry is the hallmark of a typical gunshot wound at intermediate or distant range. Contact wounds may have muzzle impression or stellate tearing.

Blackening (soot), tattooing/stippling (unburnt powder particles), and singeing of hair indicate the gun was fired at close range (within ~30–90 cm) — products of combustion reach the skin.

Range estimation hierarchy: contact → muzzle mark/blast tear/soot; near contact → soot + tattooing; intermediate → tattooing only (soot absent); distant → entry wound only with abrasion collar, no powder effects.

Soot deposition, tattooing, and singeing are signs of close-range firing. At distant range (>90 cm) only the bullet reaches the target; combustion products dissipate.

Primary blast injury is caused by the overpressure (shock/pressure) wave. Air-filled organs (tympanic membranes, lungs, bowel) are most vulnerable to barotrauma.

Blast injury classification: Primary (pressure wave — hollow organ damage), Secondary (fragmentation — penetrating trauma), Tertiary (displacement — blunt trauma), Quaternary (burns, toxic inhalation, crush).

Primary = overpressure wave → hollow organ barotrauma. Secondary = fragments/shrapnel. Tertiary = body thrown against objects. Quaternary = burns, crush, toxic gas.

High-velocity rifle bullets fragment extensively inside the cranium, producing multiple small metallic densities — the 'lead snowstorm' sign on imaging. This indicates high-energy transfer.

In head gunshot wounds: handguns tend to produce single bullet tracks; high-velocity rifle bullets fragment (lead snowstorm); shotguns at close range produce a constellation of pellet shadows.

The 'lead snowstorm' pattern of multiple metallic fragments is classic for high-velocity rifle wounds where the bullet disintegrates after entry. Shotgun pellets produce multiple discrete round pellet shadows.

The small intestine occupies the largest volume in the peritoneal cavity and has multiple loops, making it the most frequently injured intra-abdominal organ in penetrating gunshot wounds.

Abdominal gunshot wound organ injury frequency: small intestine > colon > liver > stomach. The retroperitoneal organs (kidneys, aorta) are less often hit in standard penetrating abdominal trajectories.

Due to its large surface area and central position, the small intestine is the most commonly injured abdominal organ in penetrating trauma — followed by the colon and liver.

Steering wheel impact leaves a circular 'bull's-eye' or imprint bruise on the chest, often associated with underlying sternal fracture, rib fractures, and blunt cardiac injury.

Steering wheel injury → circular chest bruise, sternal/rib fractures, blunt aortic injury. Seatbelt injury → diagonal bruise across chest/abdomen, mesenteric tears, Chance fracture. Airbag → facial/upper limb abrasions.

A circular imprint bruise pattern on the anterior chest wall is the classic signature of steering wheel impact in unrestrained drivers. Seatbelts produce diagonal/band-shaped bruises.

Comminuted compression (crush) fractures of the calcaneum are pathognomonic of vertical deceleration forces when a person lands on their feet — commonly seen in jumpers/falls from height.

Fall-from-height triad: calcaneal fractures + lumbar vertebral burst fractures + Colles' wrist fractures. The injury pattern helps reconstruct the mode of landing in medico-legal autopsies.

Bilateral comminuted calcaneal fractures are the hallmark of 'landing-on-feet' falls from height. They are often associated with lumbar burst fractures (from axial loading up the spine) and wrist fractures (outstretched hand).

At close range, shotgun pellets have not yet fully dispersed, producing a single large ragged entrance wound with a central defect (wad mark), soot, and multiple pellet tracks on imaging.

Shotgun range estimation: <1 m = single large wound + wad mark; 1–3 m = central defect + surrounding satellite pellet wounds; >3 m = scattered individual pellet wounds without central defect.

Shotgun wounds at close range appear as one large irregular entry (pellets enter as a mass). At greater distances, pellets scatter, producing multiple small punctate entry wounds.

Brown-Séquard syndrome results from hemisection of the cord. Corticospinal and dorsal column tracts are ipsilateral → motor and proprioception loss ipsilateral. Spinothalamic fibres cross → pain/temperature loss contralateral.

Spinal cord injury syndromes: Brown-Séquard (hemisection), Central cord (motor > sensory, sacral sparing), Anterior cord (motor + pain loss, proprioception intact), Complete injury (no motor/sensory below lesion).

Brown-Séquard = hemisection. Motor (corticospinal) and vibration/proprioception (dorsal columns) are lost ipsilateral; pain and temperature are lost contralateral (spinothalamic fibres already crossed).

A 'rat-hole' or keyhole wound occurs when a bullet is tumbling (yawing) or enters sideways — creating an elongated, irregular entry wound. It can also occur when a ricochet bullet enters at an oblique angle.

Bullet yaw/tumble (spinning off-axis) produces keyhole entry wounds. Ricochet bullets lose velocity and spin, often entering laterally. Both disrupt the classic entry-wound morphology used for range estimation.

Keyhole/rat-hole wounds result from an unstabilised or tumbling bullet entering sideways rather than nose-first. This produces an elongated entry rather than a round punched-out wound.