Long Range Shooting On A Spinning Planet – The Coriolis Effect

Photo by Dustin Ellermann, Whittington Center range. The Coriolis Effect is at play when shooting extreme long-range shots, like this (2100 yards in Raton, New Mexico). During the long flight of the bullet, the rotation of the Earth actually moves the target (in space). The Earth appears very stable when you are at the range. It is actually a large sphere that zooms through space, while spinning around its own axis one full turn every 24 hour. The rotation of earth can cause problems for extreme long range shooters. The rotation of the earth can cause an apparent deflection in the bullet’s path when the flight time is extended. This is the ballistics manifestation for the Coriolis Effect. Bryan Litz, of Applied Ballistics, explains the Coriolis Effect through his Ballistics Books and Seminars. Bryan Litz notes that Coriolis “is a very subtle effect.” Coriolis is not a big deal in most shooting situations within 1K. The Coriolis Effect is less than a click at 1000 yards (for most cartridge types). In windy conditions the Coriolis Effect can be “lost” even beyond 1000 yards. Bryan says that in calm conditions and when shooting at extreme distances, you can benefit by adjusting your ballistics for Coriolis. Bryan explains that the Coriolis Effect is related to the rotation of the Earth. You are shooting from one point on a rotating globe, in an inertial frame. This can cause the bullet to appear to drift away from its target if the flight of the bullet is prolonged. The amount of apparent drift is very small. It depends on your latitude, and azimuth on the planet.” Coriolis has a very subtle impact. Coriolis is only noticeable at 1000 yards with typical bullet BCs and speeds. Bryan advises that you should not think about Coriolis when shooting at moving targets or in high-uncertainty wind environments. There are too many variables to consider, and Coriolis will only distract you. Coriolis will creep in when you are shooting at a long range, with small targets, and under low-wind conditions. If you include Coriolis in your ballistics calculations, you’ll get more precision and accuracy. Coriolis is not important in most practical situations of long-range shooting. What’s important is knowing when to consider it and when not to. When applying it will be important and when it won’t.”