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YouTube: VIDEO: Gunwerks: Demonstrating how Coriolis effects bullet drop at 1000 yards

May 30, 2013

YouTube:  VIDEO:  Gunwerks:  Demonstrating how Coriolis effects bullet drop at 1000 yards



{ 10 comments… read them below or add one }

Hugh Phillips May 30, 2013 at 9:22 am

I was taught in the Marine Corps to first fire a group, then adjust windage and elevation. We heard nothing about the Corealis effect but it seems to me that our primitive method worked very well.


Jim S June 28, 2013 at 9:17 am

I agree with Hugh and also came up through the Marine Corps system. You fire a group, adjust and then fire again. Except for wind, which can be variable, you have the correct “dope” on your rifle. This corealis effect is too esoteric and down in the weeds to worry about. Besides, other than snipers and high-power competitors, no one shoots at 1000 yards.


J Turgeon May 30, 2013 at 1:29 pm

Not mentioned is the same effect when shooting north & south— the earth turns as the bullet travels & if shooting East it would seem that the gun to target delay would cause a hit to the left of the bull & to the west the trajectory & time/distance would carry to the right.


Buggy May 30, 2013 at 4:51 pm

Coriolis or not, that’s still some good shooting for 1000 yards. Good job.


Mindflayer June 26, 2013 at 11:34 pm

Cool stuff.

Allow me to be “that guy”… it should be “Demonstrating how Coriolis affects bullet drop at 1000 yards” or “Demonstrating the Coriolis effect on bullet drop at 1000 yards”.


John T. June 27, 2013 at 9:29 am

Hmmm. Because the earth spins at the same speed, and the air is carries at about the same speed generally, and the rifle is moving with the earth which means the bullet in the rifle is moving with the earth, shouldn’t the bullet be traveling at the same speed as the earth spins when it leaves the barrel? I think that the difference between groups can be explained by the small air drift that the bullet passes thru as it travels toward the target. In one direction, the air movement would cause the bullet to climb due to its rotation, and in the opposite direction, the air movement may cause the bullet to drop. Just trying to apply basic physics and ballistics to this video. Good shooting nonetheless thru moderate mirage.


Marvin Shoaf June 27, 2013 at 9:31 am

I might consider the validity of this theory, had the firearm been fired from a fixed rotation base, on a fixed bench rest with theodolite precision and the targets precisely level with each other. The heat radiation of both surfaces must be exactly the same. (this is impossible to obtain over the terrain shown) With ammo that is exactly the same. Unless the forgoing is done the Coriolis theory is but an exercise in mental masturbation.


Moses June 28, 2013 at 2:20 pm

If I shoot west, the earth is rotating TOWARDS me so I would expect the distance to close faster meaning my bullet should not drop as much and my groups be higher. If I shoot east the earth is moving AWAY from me furthering the distance and would expect my bullets to group lower – exact opposite of this shooter’s results.

As for shooting north and south – objects in motion tend to remain in motion. I shoot north my gun and bullets are already traveling with the earth’s rotation to the east. When I shoot, my bullet is already traveling east with the rotation. The only thing that will have much effect at this point is the wind.

Throw an object out of your car window at a 90 deg angle from the direction of travel – it will continue in the direction of travel slowing from the forward direction mostly from the impedance of the wind.


anonymous January 16, 2014 at 2:08 am


Imagine the earth is two vehicles on the highway. Imagine you are on the leading car shooting at the chasing car. Both vehicles are traveling at the same speed. Since they are both traveling at the same speed the distance doesn’t change and the time to hit doesn’t change.

Your target and your gun are both moving at the same speed. Just like with the car example, the “earth moving towards you” is cancelled out by you “moving away from the target”.

As for shooting north and south, you should need to aim a bit low for both, but not as much as when shooting west. You have to remember that the earth is curved, so even though the bullet is following the speed of the earth, it still has to follow a straight line after it leaves the gun. Say you are shooting north. The bullet, gun and target are all moving right at the same speed before firing. After firing, the bullet is moving to the right in a straight line. The gun and the target are not moving in a straight line, since the earth is curved, the target and you will move down a bit, which will cause the bullet to hit higher.

It’s more pronounced when firing east and west because since the target is further away, it moves either up or down faster. When it’s North and South it’s mostly negligible because you don’t move up or down as fast. Imagine you are looking at a beach ball rolling towards you. the very top is not moving down very fast, it’s moving towards you. The side of the ball on the other hand is moving down very fast.

Source: College student that enjoys math and physics


Chris April 9, 2014 at 4:15 am

John T. hit the mark. While the Gunwerks range experiment is a good example of the “Eotvos” effect, their explanation is wrong.
From a recent article in The Arms Guide:
“Despite being associated with Coriolis, the phenomenon that actually affect the vertical component of the trajectory is called Eötvös Effect. The rotation of the Earth generates a centrifugal force, the same that pushes you to the side when you make a sharp turn with your car. This force act perpendicular to the Earth rotatory axis, adding or subtracting to the gravity force. When an object flies eastward, in the same direction of Earth’s rotation, centrifugal force acts opposite of gravity, pushing it away from the Earth’s surface. If the object flies westward, in the opposite direction of the Earth rotation, centrifugal force pushes the object toward the ground concurrently to gravity force. Thus, bullets fired to the east always fly a little higher, and, conversely, bullets fired to the west always travel somewhat low.”

Full article: http://thearmsguide.com/5329/external-ballistics-the-coriolis-effect-6-theory-section/

Why do you think NASA uses Florida for most of its launches? Do you think NASA engineers picked the location because of the scantily clad women in Florida? Well ok, that may be the real reason, but the scientific reason NASA gives is the Eotvos effect. The linear velocity of the earth at the equator is 1,070 mph or about 1,600 fps. That makes it easier to reach the roughly 25,000 mph needed to achieve escape velocity. The earth’s linear velocity is at its maximum at the equator and falls to near zero at the poles. NASA saves fuel by taking advantage of this effect. BTW, NASA launches its rockets to the east.

With that said, as a fellow Marine, I have to agree with Hugh and Jim S. If you have the luxury of shooting spotting shots, then you can forget about all of these “nuisance” factors like coriolis, eotvos, humidity, elevation, etc. However, if you have to take a cold-bore shot, its best to account for these effects.


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