Enter Bullet Data
Formula Used
Weight in pounds: Bullet Weight ÷ 7000
Sectional Density: Bullet Weight in Pounds ÷ Diameter²
Ballistic Coefficient: Sectional Density ÷ Form Factor
Muzzle Energy: Bullet Weight × Velocity² ÷ 450240
The calculator uses the standard sectional density method. The result is an estimate. Real drag tables, air density, bullet shape, and velocity bands can change field values.
How to Use This Calculator
- Enter bullet weight in grains.
- Enter bullet diameter in inches.
- Add the form factor for your chosen projectile shape.
- Select a drag model, such as G1 or G7.
- Enter velocity, distance, and wind speed.
- Press the calculate button.
- Review the result above the form.
- Use CSV or PDF buttons to save the result.
Example Data Table
| Weight | Diameter | Form Factor | Sectional Density | Estimated BC |
|---|---|---|---|---|
| 150 gr | 0.308 in | 1.00 | 0.226 | 0.226 |
| 168 gr | 0.308 in | 0.82 | 0.253 | 0.309 |
| 175 gr | 0.308 in | 0.70 | 0.264 | 0.377 |
| 140 gr | 0.264 in | 0.62 | 0.287 | 0.463 |
Bullet Ballistic Coefficient Guide
What This Calculator Does
A ballistic coefficient describes how well a bullet keeps speed while moving through air. It compares bullet mass, diameter, and shape efficiency. A higher value usually means less drag. It also means better velocity retention. This calculator gives a practical estimate from common bullet data. It is useful for study, comparison, and record keeping.
Why Sectional Density Matters
Sectional density links bullet weight with diameter. A heavier bullet with the same diameter has greater sectional density. That often improves momentum retention. Diameter also matters because frontal area creates resistance. The calculator first converts grains into pounds. Then it divides that value by the square of bullet diameter.
Role of Form Factor
Form factor adjusts the result for bullet shape. Sleek bullets usually use a smaller form factor. Blunt bullets usually use a larger value. When the form factor decreases, the ballistic coefficient rises. This does not make the estimate perfect. It only provides a cleaner comparison.
Using G1 and G7 Models
G1 and G7 are reference drag models. G1 is common for flat base bullets. G7 is often used for long boat tail shapes. The selected model helps label your result. The numeric formula here still depends on sectional density and form factor. For exact flight work, use tested maker data.
Reading the Result
The result table shows coefficient, energy, time estimate, and wind drift index. These values help compare several bullet designs. They should not replace verified range data. Weather, altitude, muzzle speed, twist, and measurement errors affect real motion. Use this calculator as a planning and learning tool. Keep notes from each calculation.
FAQs
What is ballistic coefficient?
Ballistic coefficient is a number that estimates how efficiently a bullet moves through air. A higher value usually means lower drag and better velocity retention.
Which units should I enter?
Enter bullet weight in grains and diameter in inches. Velocity should be entered in feet per second, while distance should be entered in yards.
What is sectional density?
Sectional density compares bullet weight with diameter. It is found by dividing bullet weight in pounds by the square of bullet diameter.
What is form factor?
Form factor compares the bullet shape with a standard drag model. A lower value usually means the bullet shape is more efficient.
Is G1 or G7 better?
G1 is common for many traditional bullet shapes. G7 is often better for long boat tail bullets. Use the model that matches your projectile.
Why does velocity appear here?
Velocity is used for energy and time estimates. The core coefficient formula mainly uses weight, diameter, and form factor.
Can I export my result?
Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple printable report.
Are these values exact?
No. They are practical estimates. Actual values depend on tested drag data, air conditions, velocity range, and bullet manufacturing details.