Firing Solutions and DOPE, in Plain English
A "firing solution" is the answer to one question: at this distance, in this wind, with this load, where does the bullet actually hit? Two numbers fall out: how much you dial up (elevation) and how much you hold or dial off-center (wind).
This page covers what those numbers mean, how a solver computes them, why your confirmed real-world data beats any solver, and how BrassTracker exports a DOPE card you can hand to a Strelok or Applied Ballistics user.
The Two Numbers That Matter
Every shot past about 200 yards needs two corrections:
- Elevation. How much the bullet has dropped from the line of sight by the time it crosses the target. Reported in MOA, mil, or inches per hundred yards.
- Wind. How much sideways drift a crosswind will impart between muzzle and target. Reported in the same units, usually given per 10 mph reference.
Everything else (muzzle velocity, BC, atmospherics, sight height, zero distance, time of flight) is input. Those two numbers are output. A serious shooter wants the output, fast, when the rifle is hot.
What the Solver Does
A modern ballistic solver integrates the trajectory in small time steps from muzzle to target. At each step it:
- Subtracts gravity (constant pull down).
- Subtracts drag (proportional to velocity squared, scaled by the bullet's BC against a reference drag model, G1 for flat-base bullets, G7 for long boat-tail match bullets).
- Adds the crosswind component (proportional to time of flight).
- Records the position so the chart at the end has a row for every range step.
Out the back you get a drop chart: range, velocity, drop, wind, time of flight. The "firing solution" is just the row at your target distance.
Why Confirmed DOPE Beats the Solver
Solvers are predictions. They depend on:
- A muzzle velocity that's actually true for today's temperature and powder lot.
- A BC the manufacturer published, which is usually a little optimistic.
- Atmospherics you may have estimated wrong.
- A barrel that may behave a few percent differently than the model expects.
Confirmed DOPE is what you actually shot. You fired at 600 yards, hit 9 inches low, dialed 1.5 mil up to put the bullet on target. That's reality. BrassTracker's Firing Solution screen prefers a confirmed point within 5 yards of your target distance over the solver, every time.
The whole reason the app has a Confirmed DOPE log is to build that table out range by range, so the solver becomes a fallback for new distances.
Truing: Bending the Solver to Match Reality
Truing is the practice of adjusting MV (most often) until the solver's prediction matches a confirmed hold at distance. If your chrono said 2,750 fps but your real 600-yard hold matches the prediction at 2,720 fps, you "true" to 2,720 and now the solver is calibrated for the rest of the chart.
Faster than re-chronographing in changing weather, and often more accurate (a chronograph reads the bullet 5 to 15 feet ahead of the muzzle; the bullet has already shed velocity by then).
BrassTracker has a dedicated truing screen that does the bisection for you: pick a confirmed point, pick the unit, the app finds the MV that matches.
DOPE Card Export
A DOPE card is a printable cheat sheet with the drop chart for one rifle, one load, one zero. BrassTracker exports three formats from the Firing Solution screen:
- PDF. Four by six inches, black on white, prints flat. Slips into a stock pocket binder. Range, velocity, MOA drop, mil drop, inches drop, wind per 10 mph, time of flight. Confirmed points show in green with a checkmark.
- Strelok Pro JSON. Imports as a custom rifle profile in Borisov's Strelok Pro on iOS or Android. Includes the full drop table.
- Applied Ballistics JSON. Imports as a profile in AB Mobile or syncs to a Kestrel 5700 Elite. Includes any confirmed truing points so AB can use them as overrides.
Hit the share icon on the Firing Solution screen. All three files generate at once; pick what your buddy uses.
What the Card Will Not Tell You
- Cosine angle (uphill or downhill shooting). Use a rangefinder or angle indicator.
- Spin drift past 600 yards. Your solver may model it; the card prints the steady-state drift baked in. For practical shots under 1,000 yards this is usually under 0.2 mil.
- Coriolis. Real, but tiny inside 1,000 yards. AB Mobile and most Kestrel solvers can include it if you care.
When to Update the Card
Reprint when any of these change:
- Powder lot.
- Bullet lot or bullet model.
- Zero (after a re-zero, especially after dropping the rifle).
- Suppressor on or off.
- Barrel above about 600 rounds (modern barrels' velocity drifts by then).
Otherwise the card is a multi-month tool. Print it once, fold it once, shoot.