# The Coriolis effect affecting snipers.

In Cecil’s column, “How does the earth’s rotation affect the path of a bullet?” he discussed the Coriolis effect. This led to some light discussion and a thread discussing the calculations. There was also a thread General Questions recently.

Having read all of the above, I believe snipers take the Coriolis effect into account when shooting long distances. I also believe that we’ve never heard a sniper confirm this explicitly. A recent episode of Mythbusters was trying to determine whether a human could dodge a bullet fired directly at them. During the aftershow Jamie said that they took the Coriolis effect into account. Apparently they also had to account for the rotation of the bullet imparted by the rifling of the barrel. That certainly came as a surprise. The sniper was up to 1200 yards from his target.

So, Una Persson, it looks like your math holds up in real life. Pretty cool, no?

Well, I’d have to see what they did (I can’t get the video to open until I get home), but it sounds interesting!

The link I included was to an after show wrap-up on the Discovery site. There are some other videos for that episode accessible from that link. The episode was named “Dodge a Bullet” and it was the eighth episode of the ninth season.

Jamie mentioned everything except the Coriolis effect in the episode proper; I was so ticked, especially after the long discussions here. Glad he mentioned it in the aftershow.
Powers &8^]

At long range, coriolis effect IS of significance.
Want to talk about shooting 300 yards? Not highly significant. But, the MOA errors build approaching a half mile and longer.
I’d have to do some digging to find the formulae used for the ballistic calculators and removing the ballistic coefficient of the round for the base formula…
I remember reviewing it once, it gave me a headache that special relativity didn’t…

Using this ballistic calculator, I observe the following:

Round: .308 175gr 2600fps
Shooting north at 35 degrees north latitude

Effect of Coriolis force at 300 yds: 0.4 in
Effect of Coriolis force at 600 yds: 2.4 in
Effect of Coriolis force at 1000 yds: 10.8 in

How is that output presented? Is it given in an X and a Y offset, or just one number? What do those corrections mean, exactly?

Just curious.

IIRC, it’s because the spin of the bullet causes one side of the bullet to experience more air drag resistance to gravity than the other, leading to a lateral force.

This reminds me of a strip in the online Schlock Mercenary comic, http://www.schlockmercenary.com/2008-08-17 in which our hero discovered that firing a projectile in a rotating space habitat requires some serious fire-correction calculations. I think if we ever do have guns aboard rotating space habitats, a mini-targeting computer that can compensate for Coriolis will be standard issue.

That device allows the user to turn Coriolis correction on or off. The numbers I posted are the differences in the calculated windage corrections with and without the Coriolis correction.