What is most affected by Coriolis Effect is the horizontal component of the bullet trajectory. Because of the Coriolis effect, every moving object not connected to the ground is always deflected to right in the Northern Hemisphere, and always toward left in the Southern Hemisphere. The deflection is not east or west, but specifically to the right or left with reference to the shooting direction. It doesn’t matter in which direction you shoot; it is a function of latitude and average bullet speed. Its effect is maximum at the poles, and decreases as one moves toward the Equator, where it is minimal. The explanation of this phenomenon is more difficult than the explanation of Eötvös Effect, so I won’t go into it into detail.

Here’s an example of error due to Coriolis effect: firing the same .308 175gr bullet at 2700fps muzzle velocity, from a latitude of 45° in the Northern Hemisphere, the deflection at 1000yds will be of 3in to right. At the North Pole, where the effect is maximum, the deflection will be a little more than four inches. The deflection will be the same in the Southern Hemisphere, but it will be to the left, instead.

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2 Responses to “Coriolis”

  1. sexton16 Says:

    Totally counter intuitive. Must investigate.

  2. Walter Mattson Says:

    walter mattson: I remember solving problems for the effect of Coriolis in one of my engineering classes back in 1960. I do not recall that the value stayed the same regardless of the direction of the initial movement. It appears that science is not settled. Maybe someone should tell that to the climate scientists.

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