The trajectory calculator

Pick ammo (best) and a firearm chambered for it, or enter everything manually. The solver integrates the drag/gravity equations against the standard G1/G7 tables — or your custom drag function — and reports drop, windage, velocity, energy, and time per range. Inputs are grouped by kind: the static ammo & firearm setup, and the conditions on the day.

Shot solution

The field answer to “what do I dial?”: enter the exact distance to your target and get the elevation and windage to dial (in your scope’s clicks when a scope is set), plus the velocity, energy, Mach and time of flight at that range. It’s the same physics as the full table, evaluated at your one range.

What the columns mean

• Dial shows the correction in your scope’s clicks (deflects left → dial Right).
• The windage columns show the deflection with L/R letters.
• The ±1 SD column shows what your measured velocity spread costs vertically at each range — from your own chronograph SD. It’s a floor, not a ceiling (BC variation and wind reading add more).

Wind, twist, and spin drift

• Wind is set by a direction knob or the angle field: 0° is a headwind (12 o’clock), 90° is from the right (3 o’clock) and pushes the bullet left.
• Twist rate and direction: enter the twist (inches per turn, e.g. 1:8) and whether the rifling is right- or left-hand — direction matters, not just the rate, and the Right/Left picker alone (no rate) leaves spin drift off. Right-hand twist drifts the bullet right.

Stability (SG)

Stability is computed by the Miller rule when twist, bullet dimensions, and mass are known:

• Below 1.0 the bullet is unstable.
• 1.0–1.5 is marginal (the BC you paid for degrades).
• 1.5+ is comfortable.

If the bullet length was estimated (4.2 × caliber), the readout says so — measure your bullet for a real answer.

Optional physics

Optional inputs engage optional physics: latitude (+ azimuth) turns on Coriolis; density altitude replaces temperature/pressure/humidity as a single number. Rows going transonic are flagged — the model is least trustworthy exactly there.