Ballistic Coefficient Calculator

Calculate the ballistic coefficient of projectiles based on weight, diameter, and length. Supports both metric (g, mm) and imperial (gr, in) units.

About Ballistic Coefficient Calculator

Understanding Ballistic Coefficient

The ballistic coefficient (BC) is a measure of a projectile's ability to overcome air resistance during flight. It combines the projectile's mass, diameter, and shape into a single number that helps predict its trajectory and behavior in flight. A higher BC indicates that the projectile is more aerodynamic and will better maintain its velocity.

The concept of ballistic coefficient was developed in the late 19th century as part of efforts to understand and predict projectile trajectories more accurately. Today, it's a crucial parameter in both archery and firearms, helping archers and shooters select the most appropriate projectiles for their intended use.

Key Components of BC:

Sectional Density (mass to cross-sectional area ratio)
Form Factor (shape efficiency)
Standard Reference Projectile (G1, G7, etc.)
Environmental Conditions
Velocity Ranges

The Mathematics of Ballistic Coefficient

The ballistic coefficient calculation involves several key parameters and equations that help quantify a projectile's aerodynamic efficiency. Understanding these calculations helps in selecting optimal projectiles for specific applications.

Calculation Components:

1. Sectional Density (SD):

SD = Weight / (Diameter²)

2. Form Factor (i):

i = 0.9 + (Length/Diameter × 0.05)

3. Ballistic Coefficient:

BC = (SD × i) / Form Factor

BC Models and Standards

Different ballistic coefficient models exist for various projectile types. The most common are the G1 and G7 standards, each optimized for different projectile shapes:

G1 Standard

• Flat-based spitzer shape
• Most common reference standard
• Suitable for traditional bullets
• Used for most hunting ammunition
• Historical standard since 1880s

G7 Standard

• Boat-tail projectile design
• Better for modern long-range bullets
• More accurate at high velocities
• Preferred for precision shooting
• Modern standard for match grade ammo

Practical Applications

Target Shooting

• Trajectory prediction
• Wind drift compensation
• Range estimation
• Competition selection
• Equipment optimization

Hunting Applications

• Terminal performance
• Effective range determination
• Game-specific selection
• Environmental considerations
• Ethical shot placement

Typical BC Values

Common BC Ranges by Projectile Type

Projectile Type	Typical BC Range	Common Applications
Target Arrows	0.200 - 0.300	Competition archery
Hunting Arrows	0.150 - 0.250	Game hunting
Match Bullets	0.500 - 0.800	Long-range shooting
Hunting Bullets	0.300 - 0.500	General purpose

Frequently Asked Questions

How does BC affect projectile trajectory?

A higher BC means the projectile is more aerodynamic and will maintain its velocity better over distance. This results in a flatter trajectory, less wind drift, and better retention of energy at longer ranges. Lower BC projectiles will experience more drag and drop more quickly.

Why are there different BC models (G1, G7, etc.)?

Different BC models exist because projectiles come in various shapes and designs. The G1 model was based on shorter, flat-based projectiles common in the past, while G7 better represents modern boat-tail designs. Each model provides more accurate predictions for specific projectile types.

Is a higher BC always better?

Not necessarily. While a higher BC generally means better aerodynamic performance, other factors like intended use, terminal performance, and practical considerations matter too. For example, hunting projectiles might sacrifice some BC for better expansion and energy transfer on impact.