Sectional Density (SD)
Definition
The ratio of a bullet's mass to the square of its diameter. Higher SD values predict greater penetration depth in a given medium because the projectile presents less frontal area per unit of driving mass. Used in penetration models by DSTL, FBI Ballistic Research Facility, and Indian CFSL.
Related terms
- 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...
- 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...
- 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...
Explained in
- Penetration Mechanics and the Hydrostatic-Shock ModelThe ratio of a bullet's mass to the square of its diameter. Higher SD values predict greater penetration depth in a given medium because the projectile present...