Permanent Cavity
Definition
The lasting wound channel produced by the bullet's direct crushing and laceration of tissue. Diameter approximates expanded projectile diameter. At handgun velocities, this is the dominant injury mechanism. Visible at autopsy dissection.
- Visibility
- Visible at autopsy dissection
- Dominant at
- Handgun velocities, the primary injury mechanism
- Diameter approximates
- Expanded projectile width (JHP) or calibre (FMJ)
Common questions
What exactly is a permanent cavity?+
It is the wound channel crushed or lacerated directly by the bullet as it travels through tissue. The diameter roughly matches the expanded width of a hollow-point bullet or the calibre of a full-metal-jacket round. Unlike the temporary cavity (which collapses), the permanent cavity persists and is visible during autopsy dissection.
How does permanent cavity differ from temporary cavity?+
The permanent cavity is the lasting tissue destruction caused by direct bullet contact, while the temporary cavity is a temporary expansion of tissue around the wound track that collapses afterward. At handgun velocities, the permanent cavity is the dominant injury mechanism because the tissue damage it causes is the main driver of harm.
Does the size of the permanent cavity change based on ammunition type?+
Yes. A full-metal-jacket bullet creates a permanent cavity roughly equal to its calibre. A hollow-point bullet that expands creates a larger permanent cavity because the expanded diameter is wider than the original bullet diameter. The expanded hollow-point produces more crushed tissue and a correspondingly larger wound track.
Related terms
- Temporary Cavity
- The transient radial tissue displacement produced by a bullet's passing. Caused by the transfer of kinetic energy to surrounding tissue via compression...
- Abrasion Collar
- The rim of abraded, dried skin surrounding a gunshot entry wound, produced by the bullet stretching the skin inward before perforation. Width...
- Accidental Discharge
- Unintended firing of a weapon without a deliberate trigger pull, usually caused by mechanical defect, sear wear, drop impact or unsafe handling.
- Ballistic Coefficient (BC)
- The ratio of a projectile's sectional density to its drag relative to a reference standard (G1 or G7). Higher BC means less...
- Blow-Out Exit Wound
- A large, ragged exit wound with radiating lacerations produced when the bullet retains high residual kinetic energy at exit and the skin...
- Choke (Shotgun)
- Constriction at the muzzle of a shotgun barrel that controls pellet spread. From most-open to most-tight: cylinder, improved cylinder, modified, full choke.
- Deflagration
- A subsonic combustion front propagating through an explosive by thermal conduction. Characteristic of low explosives such as black powder and smokeless powder;...
- External Ballistics
- Study of bullet flight from muzzle to target. Governed by gravity, air drag, wind, spin-stabilisation, Magnus effect and (at long range) Coriolis...
- FBI 10% Gelatin Protocol
- The standard medium for law-enforcement ammunition testing, adopted after the 1986 Miami shootout. Ten percent by weight porcine gelatin calibrated with a...
- Grease Ring
- A grey-to-black discolouration at the outer margin of the entry wound's abrasion collar, caused by lubricant and metal fouling on the bullet...
- Hydrostatic Shock
- The contested hypothesis that a high-velocity bullet generates a remote pressure wave through body fluids sufficient to produce immediate neurological incapacitation without...
- Internal Ballistics
- Study of what happens inside the firearm from primer ignition to bullet exit at the muzzle. Includes propellant combustion, gas pressure, bullet...
Explained in these topics
- Internal, External and Terminal Ballistics: BasicsTissue actually crushed and destroyed by direct bullet contact along the wound track. Roughly the bullet diameter for an FMJ, larger for an expanded JHP.
- Penetration Mechanics and the Hydrostatic-Shock ModelThe lasting wound channel crushed or lacerated directly by the projectile. At handgun velocities this is the dominant injury mechanism. Diameter approximates t...
- Velocity, Penetration, Dispersion, Ricochet and Accidental DischargeThe crushed tissue track left by the bullet itself. Roughly cylindrical, slightly larger than calibre, persists in the gelatin block after the bullet has stopp...
- Wound Ballistics: Entry Wounds, Exit Wounds and CavitationThe lasting wound channel produced by the bullet's direct crushing and laceration of tissue. Diameter approximates expanded projectile diameter. At handgun vel...