Hatcher Rule
Definition
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 from the Litz model by 10-20% beyond 600 m.
- Source
- Hatcher's Notebook, 1947
- Author
- Major General Julian Hatcher
- Use
- Field wind-drift estimation, courtroom cross-reference
- Accuracy
- Diverges from the Litz model by 10 to 20 percent beyond 600 m
Common questions
Why would a modern ballistics report cite a 1947 formula alongside contemporary models?+
The Hatcher rule offers a quick, hand-calculable cross-check against modern computer ballistic models like the Litz method, and showing both can help demonstrate a trajectory estimate holds up rather than depending on one software tool.
Why does the Hatcher rule diverge more from modern models at longer range?+
It was derived as a simplified approximation without accounting for the more complex drag and Coriolis effects that dominate at extended distances, so its accuracy holds reasonably well at shorter range but widens as distance increases.
Is the Hatcher rule still used for actual long-range trajectory reconstruction in casework?+
Modern ballistic reconstruction relies on software models with measured ballistic coefficients for precision work, and the Hatcher rule now mainly serves as a fast sanity check or a simplified explanatory tool in court.
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...
- 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...