Aerodynamic Drag
Definition
The retarding force exerted by air on a moving projectile. Proportional to air density, the square of velocity, the drag coefficient, and the bullet's cross-sectional area. Dominates deceleration for supersonic rifle projectiles.
- Depends on
- Air density, velocity squared, drag coefficient
- Also depends on
- Bullet cross-sectional area
- Effect
- Retards projectile motion
- Dominant regime
- Supersonic rifle projectiles
Common questions
Why does drag scale with velocity squared rather than velocity itself?+
Drag in this regime comes from momentum transferred to displaced air, and both the rate of air encountered and the momentum per encounter increase with speed, so the two effects combine into a square relationship.
How does ballistic coefficient relate to aerodynamic drag in casework?+
Ballistic coefficient summarises how efficiently a bullet's shape and mass overcome drag, and a firearms examiner uses it to estimate velocity loss over distance when reconstructing a shooting trajectory.
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...
- Drag Coefficient (C_D)
- A dimensionless number characterising the aerodynamic drag force relative to the dynamic pressure and the projectile's cross-sectional area. Varies with Mach number;...
- G1 Drag Standard
- The Gavre Commission reference projectile: flat base, round-nose ogive. Established in the late 19th century and codified at Aberdeen Proving Ground. Standard...
- G7 Drag Standard
- A long, boat-tailed secant-ogive reference projectile developed by Bryan Litz at Applied Ballistics. More accurate for modern spitzer-BT precision and military rifle...
- Hatcher Rule
- A simplified wind-drift estimation formula from Major General Julian Hatcher's Hatcher's Notebook (1947). Useful as a field check and courtroom cross-reference; diverges...
- Litz Wind Drift Model
- The velocity-integrated wind-drift calculation method from Brian Litz's Applied Ballistics for Long Range Shooting (2015), implemented in AB Quantum and Hornady 4DOF....
- Sectional Density
- A bullet's mass divided by the square of its diameter (in consistent units). A component of BC; higher sectional density generally produces...
- Transonic Regime
- The velocity range from approximately Mach 0.8 to 1.2 (272 to 408 m/s at sea level, 15 degrees C). Wave drag peaks...
- Wind Drift
- Lateral deflection of a bullet by a crosswind component. Grows with time-of-flight (faster than range) and is the most variable error source...