Calculate bullet ballistic coefficient (G1 & G7 BC = SD/i), sectional density (SD = m / 7000·d²), form factor, and atmospheric density corrections with the free Ballistic Coefficient Calculator.
G1 Equivalent: ~0.646 • Sectional Density: 0.287 lb/in² • Form Factor: 0.880
\(m / 7000 d^2\) (\(\text{lb/in}^2\))
ICAO Sea Level (1.00x)
Relative to standard
Mach 1.2 threshold
74.3% initial speed
10 mph 90° crosswind
In external ballistics and rifle shooting, the Ballistic Coefficient (BC) is an aerodynamic figure of merit that quantifies a bullet's efficiency in overcoming atmospheric drag resistance during flight:
A projectile with a high ballistic coefficient cuts through the atmosphere cleanly, decelerating far more slowly than a low-BC bullet. As a result, high-BC bullets reach extreme downrange distances in shorter flight times, experience substantially less trajectory drop, resist crosswind deflection, and deliver higher terminal impact energy onto target.
| Drag Model | Reference Bullet Geometry | Best Applications |
|---|---|---|
| G1 Standard | Flat-base bullet, 2-caliber blunt tangent ogive | Handgun, rimfire (.22 LR), flat-base hunting bullets |
| G7 Standard | 7.5° boat-tail, 10-caliber secant/tangent ogive | Modern long-range boat-tail rifle bullets (6.5 Creedmoor, .308, .338) |
Because G1 drag curves differ drastically from streamlined boat-tail bullets at transonic velocities (\(\text{Mach } 1.2 \to 0.8\)), a G1 BC rating shifts across speed. Conversely, a G7 BC remains virtually constant across the entire supersonic flight envelope, providing vastly superior trajectory accuracy for extreme long-range solvers.
Choose between Physical Dimensions (Mass, Caliber, Form Factor) or 2-Point Chronograph Velocity Decay.
Enter bullet weight in grains or grams, and bullet caliber diameter in inches or millimeters.
Select G7 for modern long-range boat-tail bullets or G1 for flat-base handgun and short-range projectiles.
Inspect sectional density, atmospheric density correction factors, supersonic range limits, and live KaTeX mathematical derivations.
Converts confusing manufacturer G1 ratings into accurate, constant G7 ballistic coefficients for precision long-range match solvers.
Scales standard ICAO sea-level BC ratings to thin mountain air and varying temperatures for accurate high-altitude hunting DOPE cards.
Calculates true experimental BC from two downrange chronograph readings for wildcat and custom handloaded rifle cartridges.
Seamlessly toggles between historical G1 and modern military/match G7 reference projectiles.
Extracts experimental ballistic coefficients from measured muzzle velocity and downrange radar speeds.
Dynamically adjusts for temperature, barometric pressure, and altitude density scaling.
Why under-stabilized bullets suffer severe ballistic coefficient degradation:
A bullet cannot achieve its full advertised ballistic coefficient if it is marginally stabilized. According to the Miller Twist Rule, precision rifle shooters require a Gyroscopic Stability Factor (\(S_g \ge 1.50\)) for long-range match performance. If a barrel twist is too slow (e.g., shooting a long 147gr 6.5mm bullet through an old 1:10" twist barrel instead of a fast 1:8" twist), the bullet flies with high yaw and pitch angles, increasing effective drag and reducing real-world BC by \(5\%\) to \(20\%\).
How modern acoustic and radar technology measures drag decay in real time:
Traditional optical light-screen chronographs capture velocity only at fixed points (e.g., muzzle and 100 yards). Modern Doppler Ballistic Radars (such as LabRadar and Garmin Xero C1) track the bullet continuously at 100,000+ samples per second from the muzzle to 100+ yards downrange, measuring exact instantaneous deceleration (\(\frac{dv}{dt}\)) to generate point-by-point drag curves (\(C_d\) vs. Mach number) without optical shadow errors.
Comprehensive answers to common questions about ballistic coefficients, G1 vs. G7 drag models, sectional density calculations, and chronograph velocity decay.
