Quarry Ballistics — drop and wind, trued to your rifle.

Enter your bullet, velocity, and zero. Get a drop and wind chart for today's actual conditions — then shoot, tell it where the bullet really hit, and it calibrates the model to your rifle. Saves to your phone, works with no cell signal.

Take it to the range: open this page in Safari, tap Share, then Add to Home Screen. It installs like an app and works fully offline.

1 · Rifle & load

2 · Today's conditions

Wind from (clock, 12 = head-on)

3 · Chart

Dope card

4 · True it to your rifle

Shoot a group at a known distance. If your predicted correction didn't center it, enter the correction that actually worked and the solver back-figures what your rifle is really doing. Inside ~600 yd that error is almost always muzzle velocity; past that, true BC instead (with velocity already trued).

How the math works

This is a point-mass ballistic solver — the same physics behind the established ballistic apps. Your bullet's deceleration is computed against the industry-standard G1 or G7 reference drag curves, scaled by its ballistic coefficient, in air whose density comes from your temperature, pressure, and humidity (CIPM-2007 formulation — the same used by metrology labs). The trajectory is integrated step by step (Runge–Kutta), not looked up from tables. Output has been verified against an established open-source ballistics engine to within a tenth of an inch at 1,000 yards.

Why truing beats a perfect data sheet

Box velocity is optimistic, chronographs disagree, BCs are measured in someone else's barrel, and your scope's clicks aren't exactly true. Every serious long-range shooter reconciles the calculator with observed impacts — that's all truing is. Shoot at a known distance, enter the correction that actually centered the group, and the solver adjusts muzzle velocity (or BC at long range) until prediction matches reality. From then on the whole chart carries that calibration.

What this can't know: the wind between you and the target (it uses your read, and wind is the hard part), spin drift and Coriolis (not modeled — they matter past ~800 yd), and whether your scope tracks true. A calculator is a starting point; trued impacts are data.

Where do I find my numbers?

BC and weight are printed on the ammo box or the bullet maker's site — use the G7 value for boat-tail match bullets if one is published. Muzzle velocity: a chronograph if you have one; otherwise start from the box value and let truing correct it. Station pressure is the absolute reading from a Kestrel or weather app (not sea-level-corrected barometer); if unsure, switch to altitude and it uses the standard atmosphere.