Litz Wind Drift Model
Definition
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. More accurate than the simplified Hatcher rule at velocities below 700 m/s.
- Source
- Brian Litz, Applied Ballistics for Long Range Shooting (2015)
- Method type
- Velocity-integrated wind drift calculation
- Software implementations
- AB Quantum, Hornady 4DOF
- Outperforms Hatcher rule below
- 700 m/s
Common questions
Why does the Litz model outperform the simplified Hatcher rule at lower velocities?+
It integrates the wind's effect continuously as the bullet's velocity and time of flight change, rather than applying one averaged correction, so it stays accurate as the bullet decelerates further from the muzzle.
Where does the Litz model get applied in forensic casework?+
In long-range shooting reconstructions, to test whether a claimed shooter position and trajectory are consistent with the recovered bullet path once wind drift is properly accounted for.
Related terms
- Aerodynamic Drag
- The retarding force exerted by air on a moving projectile. Proportional to air density, the square of velocity, the drag coefficient, and...
- 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...
- 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...