Posted on 11/29/2016 11:26:22 AM PST by w1n1
You may not be taking this into Account in Precision Long Range Shooting. If you’re into long range shooting, its important to understand how the “Coriolis effect” affects your shot at 1000 yards or greater.
The Coriolis effect is the rotation of the earth and the movement of a target downrange from the shooter. This is another element that a long distance shooter has to consider for along with wind, rain, snow, distance, elevation and a many other factors. Accounting for all these factors signifies the skill sets needed for precision long range shooting.
In simple layman's term:
"if you're shooting West, your target’s gonna rotate up and towards us, which is gonna cause the bullets to hit lower."
"if you're facing east, the target's going to be dropping and slightly moving away, which is gonna cause the hits to be higher."
Jeremy from Gunwerks points out these small errors can cause huge misses at greater distances than 1000 yards if you don't pay attention to. Could be that buck that you're missing out on. See the video footage here.
The Earth moved. That’s my story and I’m sticking to it.
Well, let's see...
Earth rotates 360° in 24 hours, which is 86,400 seconds. Old-fashioned division gives us 0.0042 degrees/second, or (interestingly) fifteen seconds per second, although the first "second" is arc-seconds, and the second "second" is actual seconds.
If you take my meaning.
Anyway, during a two-second flight time, Earth moves under us 0.0084 degrees. At a distance of 1000 yards, and if you're at the equator, that's a distance of
which is a bit more than five inches! 5.27788 inches, to be more precise.
Of course, as pointed out in the article, that "movement" will be "up" if you're aiming due West, and "down" if you're aiming due East. If you're aiming North or South, there's no effect at the equator.
If you're at the North Pole, and you aim in any direction, you're aiming South. In that case, the 5+ inch error accumulates left-to-right, so you will hit a spot 5.27788 inches to the right of your aim point. The direction would be reversed at the South pole, of course.
At any point in between, you've got to bring more sines and cosines into the situation.
I knew a guy that was hired by the military in an attempt to figure out why the big ballistic missiles weren’t tracking properly. They do take into account the variable geology and topography and the resultant change in gravity. They thought it might be due to an “anti-gravity” force and he attempted to measure that in various experiments. He said the results didn’t prove anything for or against anti-gravity. I thought it was interesting that the military was interested in it, and he, being a gravity expert, didn’t dismiss the idea out of hand.
White.
As Dolly Parton always says, the right mass distribution can exert a significant attractive force:
I’m hoping that, if they secede, folks like you will come over!
If your situation precludes that, you can at least be a spy for us.
When the time is right you guys pop up out of your holes and ambush them. We'll chase them right into you.
lol. could this be why I kept missing the target at 50 yards?
I’d look at it a different way - the earth is about 24,000 miles in circumference, and rotates in 24 hours. So a point at the equator moves at about a thousand miles an hour.
A high velocity bullet will travel between about 2500 and 3200 feet per second, say roughly a mile in two seconds, or roughly a thousand yards in about a second.
1000 mph is 16 mpm or .28 mps, or approx. 1250 feet per second.
The flight of a high speed bullet to a target 1000 yards away is about a second.
In that second the target moves about 1250 feet.
Test: 1250 FPS x 60 sec x 60 min x 24hrs / 5250 feet per mile - about 20,571 miles, or within 20% of the assumed diameter of the earth.
My math skills are corroded by time, but just thinking about it, shooting east/west and vice versa, the rifle, bullet and target are all traveling in the same frame, Applying Newton’s theorums I’m not seeing how the trajectory would be affected.
Shooting north or south, coriolis effect would apply but would be greater over the equator compared to standing on one of the poles. The speed of rotation at the equator is faster than it would be either 1000 meters north or south but the variation would be small and it would take me hours to remember the math to calculate the difference.
I believe Elmer Keith or Jack O’Connor mentioned something like this causing bulls eye misses at long ranges. I did not know what he was talking about. I can barely see 100 yards with glasses!
White, with a red spot.
I have been at the equator, but don’t recall any 1,000 mph wind.
But that movement of 5.7788 inches would be lateral, almost a right angle to an imaginary stationary line radiating at a right angle from the axis of the earth. At the equator that would be a plumb line since it would radiate from the center of the earth. At any other latitude it would not be plumb since it would radiate from the same latitude on the axis.
The apparent "up" or "down" movement would be a lot less than 5.7788 inches as it would be a factor of the curvature of the earth and how much "up" or "down" deviation occurred at 1,000 yards with plus or minus 5.7788 inches of lateral movement along that arc.
The specific arc of the curvature would be different at any other latitude other than the equator as well. But then so would the lateral movement.
“My math skills are corroded by time, but just thinking about it, shooting east/west and vice versa, the rifle, bullet and target are all traveling in the same frame, Applying Newton’s theorums I’m not seeing how the trajectory would be affected.”
The target is moving up/down relative to when you pull the trigger.
The answer was hiding right there in his first seven words.
A lot of the air molecules are in geosynchronous gravitation hold, at least moving West to East...
Ok, I see that now, for shooting east and west.
The target would be rotating slower than you if you were shooting north or south away from the equator and faster if you were shooting toward the equator and that would be the true coriolis effect. I may sit down later and try to calculate that distance.
Like I’m going to pull out a paper and pencil as the thug is crawling through my window. If something is more than a 1000 yards away, I’m not going to worry too much.
Yep, but the bullet “at rest” is also moving at the same rate as the earth.
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