G7 Drag Standard
Definition
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 bullets, especially at long range.
- Origin
- One of the Gavre Commission drag functions, same era as G1, not a Bryan Litz invention
- Shape
- Long, boat-tailed, secant-ogive
- Best suited to
- Modern spitzer boat-tail and military rifle bullets
- Advantage
- More accurate long-range trajectory prediction
Common questions
When would a forensic ballistics reconstruction favour a G7-based coefficient over G1?+
When reconstructing a long-range shooting involving a modern precision rifle bullet, a G7-referenced ballistic coefficient models drag against a reference shape close to the actual bullet's form, giving a more reliable trajectory and drop estimate than a G1-based figure would.
Does using G7 eliminate the need to verify drag experimentally?+
No. G7 is still a reference standard rather than the exact bullet, so examiners ideally corroborate computed trajectories with chronograph data or known trajectory points from the actual ammunition when the case demands precision.
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...
- 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...