Question 1

What is a ballistic coefficient (BC)?

Accepted Answer

A ballistic coefficient (G1 BC) is a measure of a bullet's ability to overcome air resistance in flight. A higher BC means the bullet retains velocity better at long range. You can find BC values on bullet manufacturer packaging or in reloading manuals.

Question 2

How do I use the OpenCartridge Ballistics Calculator?

Accepted Answer

Enter your bullet's G1 ballistic coefficient, muzzle velocity, zero range, and optional atmospheric conditions (temperature, altitude, pressure). The calculator will output bullet drop, wind drift, velocity, and energy at each distance increment out to your chosen maximum range.

Question 3

What is the Rifleman's Rule for angled shots?

Accepted Answer

The Rifleman's Rule states that when shooting at an uphill or downhill angle, you should aim using the horizontal distance to the target rather than the line-of-sight distance. This calculator applies the cosine of the angle to correct your holdover for angled shots.

Question 4

How does atmospheric correction affect bullet trajectory?

Accepted Answer

Air density changes with altitude, temperature, and barometric pressure, which affects how much drag a bullet experiences. At higher altitude or temperature, air is thinner, so bullets retain velocity better and drop less than at sea level. The calculator corrects for these factors automatically.