Calculator Inputs
Example Data Table
| Pellet | Weight (gr) | Diameter (in) | Muzzle (fps) | 50 yd (fps) | Estimated BC |
|---|---|---|---|---|---|
| Sample Dome A | 8.44 | 0.177 | 870 | 730 | 0.0269 |
| Sample Dome B | 10.34 | 0.177 | 860 | 745 | 0.0315 |
| Sample Heavy C | 15.89 | 0.177 | 900 | 790 | 0.0307 |
Formula Used
Practical retained-velocity estimate:
BC ≈ (0.000085 × Rangeyd × Density Ratio) ÷ ln(Vmuzzle ÷ Vdownrange)
This page uses a practical field estimate built around measured velocity loss over a known distance. It also adjusts the estimate with air-density ratio, so hot, cold, humid, or high-pressure conditions are reflected in the result.
Supporting calculations:
Muzzle Energy = Weight × Velocity² ÷ 450240Sectional Density = (Weight in pounds) ÷ Diameter²Velocity Curve = V₀ × e-kx, wherek = ln(V₀/V₁) ÷ Range
This is a practical tuning estimate, not a laboratory drag-table replacement.
How to Use This Calculator
- Enter the pellet name for your own comparison records.
- Input pellet weight in grains and diameter in inches.
- Measure muzzle velocity with a chronograph near the muzzle.
- Measure downrange velocity at a known distance.
- Enter weather values to improve the density adjustment.
- Set a comparison BC target if you want a benchmark.
- Press Calculate BC to show results above the form.
- Review the graph, score, and export options.
FAQs
1. What does ballistic coefficient mean for pellets?
Ballistic coefficient describes how well a pellet resists drag in flight. Higher values usually retain speed and energy better, especially at longer ranges.
2. Why is pellet BC usually lower than bullet BC?
Diabolo pellets are intentionally draggy. Their waist and skirt stabilize flight, but that same shape sheds speed faster than streamlined bullets.
3. Can one pellet have different BC values?
Yes. Pellet BC changes with speed, range, and atmosphere. That is why field estimates are best compared under similar testing conditions.
4. Is a heavier pellet always better?
Not always. Heavier pellets may retain energy better, but fit, stability, barrel preference, and launch speed still determine real-world performance.
5. Why do I need downrange velocity?
A measured downrange velocity captures actual drag loss over distance. That usually gives a more useful estimate than guessing from weight alone.
6. How far should I place the second chronograph?
Many shooters use 30 to 50 yards for pellets. Pick a distance long enough to show speed loss while still producing reliable chronograph readings.
7. Does weather really matter?
Yes. Air density changes with temperature, pressure, and humidity. Denser air increases drag and can shift your practical BC estimate.
8. What makes this a “best pellet” comparison tool?
It combines BC, retention, density adjustment, and a comparison target in one page, making quick pellet-to-pellet field testing easier.