Guides · Questions shooters ask

Muzzle Wind or Target Wind? Which Part of the Path Moves the Bullet Most

We put a 10 mph crosswind in one third of a 600, 800 or 1,000 yard path at a time. The third nearest the rifle causes about half the drift, the third nearest the target about a sixth. Why, and how to weight a call.

5 min readSolved with the Ballista engineUpdated October 2026

A common question on long-range forums: “The flag at my bench says one thing and the mirage at the target says another. Which wind do I hold for?” One popular answer is that the wind near the target sets the final drift. The solver says the opposite. Put a 10 mph crosswind over only the first third of a 1,000 yd shot with a 6.5 Creedmoor, and the bullet drifts 32.2 in. Put the same wind over only the last third, and it drifts 11.1 in. Wind near the rifle moves the bullet 2.9 times as much as wind near the target.

How we split the wind

The Ballista engine takes one wind for the whole flight. To put wind in only part of the path we wrote a small point-mass integrator that follows the engine’s own equations: the same G7 drag table and interpolation, the same drag formula, fourth-order Runge–Kutta in 0.5 m steps and the same zeroing. The only change is that the air’s velocity can depend on how far downrange the bullet is. Before using it we ran both with a uniform 10 mph crosswind from 100 to 1,000 yd: the two drifts agree to within a thousandth of an inch at every 100 yd step. Spin drift and crosswind jump are left out of these numbers because they don’t depend on where the wind blows.

Near third, middle third, far third

Across both rifles and all three distances the near third causes 43–51% of the drift, the middle third 36–38% and the far third 14–19%. That’s roughly a half, a third and a sixth. The three parts add up to the full-path drift to the hundredth of an inch, so the effect of wind in different stretches simply adds.

Why the near wind counts most

A crosswind doesn’t carry the bullet. It tilts the airflow the bullet meets, and the sideways part of drag gives the bullet a small sideways velocity. What matters at the target is the angle that leaves the bullet on, and how far it then travels at that angle. The lag time article covers the uniform case.

Wind near the muzzle sets that angle early, and the bullet carries it for the whole remaining distance, so a small angle grows into a large miss. Wind near the target sets an angle with only a few yards left to act. Working against this, the bullet is slower downrange and each yard of wind there tilts its path a little more. The lever arm wins. For a wind in a short stretch at distance s, on a shot to range X:

drift ≈ wind speed × (X − s) × change in 1/velocity across that stretch

Summed over the whole path with a uniform wind, this gives back the lag-time formula exactly. We checked it against the integration: using the engine’s own velocity at each 5 yd, the formula reproduces every 100 yd band in the chart within 0.03 in.

The .308 spreads the weight a little more evenly: at 1,000 yd its near third causes 43% of the drift against 47% for the 6.5. Its bullet loses speed faster, so late wind tilts its path more, and the far part of the path counts for more. With either rifle the near third still counts the most.

Weighting a call

Say you read 10 mph at the bench, 5 mph halfway and 2 mph at the target, all full value. The plain average is 5.7 mph. Calling the target wind gives 2. The integrated drift for the 6.5 at 1,000 yd is 47.0 in, which a uniform wind of 6.9 mph would also produce. Weighting the three readings by the shares in the table (47%, 37%, 16%) gives 6.9 mph. That’s the number to hold for.

Winds that reverse along the path don’t cancel either. With 10 mph from the right over the first 500 yd and 10 mph from the left over the last 500, the 6.5 still drifts 23.6 in left at 1,000 yd, the way the near wind pushes.

What this means for your wind meter

A meter at the firing line measures the part of the path that counts most, so its reading is a good input. It isn’t the whole answer. The bench is often sheltered by a berm, a building or trees, while the bullet is out in open air a few yards in front of you. Take the reading where the bullet actually passes, then look downrange to see whether the middle of the course agrees. Mirage seen through the scope is clearest near the distance the scope is focused at, so with the parallax set on the target it shows the air at the far end, the part that counts least.

Ballista takes a single wind: one speed and one clock direction for the whole flight. Enter the weighted call, not the target wind or a plain average.

A wind-reading routine

1. Read the wind where the bullet leaves: speed and direction, full value.
2. Read the middle of the course: flags, grass, trees, mirage with the scope focused short of the target.
3. Read the target area last.
4. Weight them about half, a third and a sixth, and hold for that single number.
5. When the near and far winds disagree, trust the near one first and use the first impact to correct. The wind bracket article covers reading the miss.