Eötvös Effect

The Eötvös effect is the vertical portion of the Coriolis effect, and it depends on the compass direction of the shot rather than its azimuth alone. Firing toward the east adds a tiny bit of apparent lift, so the bullet lands marginally high, while firing toward the west does the opposite and the bullet lands marginally low. The size of the shift grows with the projectile’s speed and with how close the firing line runs to true east or west.

In practice the effect is small and only shows up at extreme distances, where it joins spin drift and the horizontal Coriolis term as a fine correction. Modern solvers fold it into the external ballistics model automatically once you enter your latitude and azimuth, so it becomes one more input rather than a hand calculation. For most shooters it stays buried inside the predicted trajectory until the targets get very far away.