Internal Ballistics
Definition
Study of what happens inside the firearm from primer ignition to bullet exit at the muzzle. Includes propellant combustion, gas pressure, bullet engraving by rifling, barrel time and recoil.
- Field
- Firearms examination
- Scope
- Primer ignition to bullet exit at muzzle
- Covers
- Propellant combustion, gas pressure, rifling engraving, barrel time, recoil
- Contrasts with
- External ballistics (flight path) and terminal ballistics (impact effects)
Common questions
Why does internal ballistics matter for toolmark identification on a fired bullet?+
As the bullet is engraved by the barrel's rifling under high pressure during internal ballistics, it picks up individual land and groove marks unique to that barrel, which is the physical basis firearms examiners rely on to link a bullet to a specific weapon.
How does barrel time affect a shot's outcome?+
Barrel time, the interval the bullet spends travelling through the barrel before exit, influences how much propellant gas pressure builds behind it and how much the muzzle can move due to recoil before the bullet leaves, both of which affect velocity consistency and accuracy.
Related terms
- 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...
- 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...
- Permanent Cavity
- The lasting wound channel produced by the bullet's direct crushing and laceration of tissue. Diameter approximates expanded projectile diameter. At handgun velocities,...
- 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...
- Terminal Ballistics
- Study of bullet behaviour at the target. Includes penetration, permanent and temporary cavity, expansion or fragmentation, yaw and tumble, energy transfer.
- Wound Ballistics
- Sub-branch of terminal ballistics dealing with biological tissue. Entry wound with abrasion collar, wound track, exit wound, hydrostatic shock in fluid-filled organs.