Muzzle Velocity
Definition
Speed of the projectile at the instant it leaves the barrel, expressed in metres per second (m/s) or feet per second (fps). Measured by optical chronograph or Doppler radar.
- Measured at
- Instant the projectile exits the barrel
- Units
- Metres per second (m/s) or feet per second (fps)
- Measurement tools
- Optical chronograph or Doppler radar
- Downstream effect
- Governs wound severity, penetration depth and range estimation
Common questions
Why does muzzle velocity matter for interpreting a gunshot wound?+
Higher muzzle velocity generally increases the kinetic energy transferred to tissue, which affects wound cavitation, penetration depth, and the likelihood of exit versus retention of the bullet. It also feeds range-of-fire and trajectory reconstructions when combined with other physical evidence.
How does an optical chronograph actually measure it?+
The projectile passes over two sensors a known distance apart just beyond the muzzle, and the chronograph times the interval between the two triggers to compute velocity as distance divided by time. Doppler radar instead tracks the projectile continuously in flight and can also show velocity decay over distance.
Does muzzle velocity stay constant once the bullet leaves the barrel?+
No, it decreases in flight due to air resistance, so velocity at impact is always lower than muzzle velocity, more so at longer ranges. Reconstructions that need striking velocity must account for this drop rather than using muzzle velocity directly.
Related terms
- Accidental Discharge
- Unintended firing of a weapon without a deliberate trigger pull, usually caused by mechanical defect, sear wear, drop impact or unsafe handling.
- 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.
- Kinetic Energy
- KE = (1/2) m v squared, where m is projectile mass and v is velocity. Doubling velocity quadruples the kinetic energy delivered...
- MOA (Minute of Angle)
- 1/60 of a degree of arc. Equal to approximately 2.908 cm (1.047 inches) at 100 m. Used in civilian and some law...
- Ordnance Gelatin
- Calibrated tissue simulant. 10 per cent gelatin at 4 degrees C is the NATO and FBI standard; 20 per cent gelatin is...
- 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,...
- Ricochet
- The deflection of a bullet off a surface at a low angle of incidence, producing a new trajectory that diverges from the...
- 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...