As the world turns fact or fiction?


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KevinR
March 21, 2010, 05:14 PM
I am sure that all of us have seen and herd in the movies that the rotation of the earth needs to be taken into account when shooting long distances.

My question is how much does the earth actually turn at 500 yds or even 1000yds. Is this even worth considering when a bullet may only be in flight 2, 5 or even 10 seconds. Or is this as I suspect, just bullskatoligy?

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Art Eatman
March 21, 2010, 05:25 PM
Aside from 16" naval shells and rockets, figure that it's "just bullskatoligy".

Quentin
March 21, 2010, 05:26 PM
Well the circumference of the Earth at the equator is about 25,000 miles and one day (rotation) is 24 hours so a point on the equator is moving about 1,000 miles an hour.

Thing is your gun and the target are lockstep, moving the same speed so I'd say forget about it and worry about what really matters like your shooting technique, breathing, ammo ballistics, the rifle/sights and weather conditions.

dagger dog
March 21, 2010, 05:33 PM
The earth turns east at approx 750 miles per hour, a British small arm committe in 1886 discovered a projectile would deviate 6" to the right (northen hemisphere, see Coriolis effect.) in 1,000 yds. Maximum drift occurs when fired toward the southwest, this effect is coupled with spindrift from the rifiling twist.

from UNDERSTANDING FIREARM BALLISTICS By Robert A Rinker

Quentin
March 21, 2010, 05:48 PM
Methinks Robert A Rinker might need to read another book on UNDERSTANDING FIREARM BALLISTICS :)

KevinR
March 21, 2010, 06:21 PM
If in fact Mr Rinker knows what he is talking about and I suspect that he does, all the rifle ranges in my area are facing the wrong direction. The state range is the worst, it faces directly south west. :barf: Just out of curiosity, what direction do other ranges of other members face?

Casefull
March 21, 2010, 06:22 PM
Not that it matters a lot but the earth is always spinning at a constant velocity. If your rifle is sighted in at 1,000 yds(ha!) then you have already taken the earths rotation into account just like you have accounted for gravity...I suppose east west shots would be affected less than north south...I give up.

R.W.Dale
March 21, 2010, 06:24 PM
The earth turns east at approx 750 miles per hour, a British small arm committe in 1886 discovered a projectile would deviate 6" to the right (northen hemisphere, see Coriolis effect.) in 1,000 yds. Maximum drift occurs when fired toward the southwest, this effect is coupled with spindrift from the rifiling twist.

from UNDERSTANDING FIREARM BALLISTICS By Robert A Rinker
I may not be a real sniper or play one on TV but my hand head ballistic computer does have an output for Coriolis effect.

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1904/es1904page01.cfm

dagger dog
March 21, 2010, 06:47 PM
Kevin,

Knob Creek Range, out side Louisville KY is where I shoot the most, and it lies somewhat southeast, and it is an old Ft. Knox military range.

Zerodefect
March 21, 2010, 07:24 PM
Since we are moving at the same speed as the earth it shouldn't matter. Rockets are leaving the Earth so it matters. I think if it made our rounds off 6" at 1000yard, we would have noticed by now.

I highly doubt Naval cannons account for the earths rotation. Do they really?

MythBuster
March 21, 2010, 07:30 PM
Yes.

Oic0
March 21, 2010, 07:34 PM
Unless I am mistaken perhaps land on the equator is moving faster than land closer to the poles, in that case it would only make a difference if firing longitudinally and over a distance long enough for it to matter?

Get what I mean? the bullet is moving the same speed as you with the earth spinning motion, fire it somewhere far away on a different plane of the axis and the bullet is still going whatever speed it was when you fired it but the objects on the ground where it ends up are moving at a different speed.

Tirod
March 21, 2010, 08:49 PM
Look up the history of the German railroad gun Big Bertha. They used it to shoot at Paris ( military targets around the outliers.) Problem was the first time they missed the impact zone selected by a significant margin. Forward observers were reporting the amount of offset and the German gunners weren't happy with their calculations - until they took into account the flight time of the projectile. What had happened was that "Paris had moved!"

Once the rotational speed of the earth is factored in, then impact is on target. As said, it's a big gun problem. At the rifle level, I doubt shooting at 1000m needs much correction.

Nonetheless, I wouldn't be surprised to find an app for that . . .

taliv
March 21, 2010, 08:51 PM
there is an app for it. in fact, even the KAC bulletflight software on my iphone takes it into account

SlamFire1
March 21, 2010, 08:55 PM
I have never noticed the earth's rotation effecting my bullets at 500 yards or 1000 yards.

I did notice that cross winds made one heck of a difference on point of impact versus point of aim. :cuss:

Now, if I was shooting at Heavy Cruisers 26 miles away, I suspect the movement of the earth under the projectile might make a difference.

aka108
March 21, 2010, 08:59 PM
It really doesn't matter. Anyone with any grey matter between their ears knows that the world is flat.

R.W.Dale
March 21, 2010, 08:59 PM
there is an app for it. in fact, even the KAC bulletflight software on my iphone takes it into account
as does my "ballistic'" app

Uncle Mike
March 21, 2010, 09:04 PM
The Coriolis Effect does indeed affect projectile flight. At the distances we normally shoot handheld firearms the effect is so small it is not a factor...but, in any event, it still does exist and affect projectiles in flight.

T.A.Sharps
March 21, 2010, 09:24 PM
The Earths rotating and moving under the bullet is true.

Yes the bullet was moving at the same speed as the Earth, but not after it left the barrel.

However,
It is an effect that only matters to long range shooters, that are changing regions of the world often. Something not likely for any one here to be dealing with, and if anyone is, they certainly already know about the physics of this.

The fix is to simply re-zero your rifle, the effect is a constant, always the same for where you are at in the world.

You would have more adjustments more often to correct that actually change all the time like temperature change, differences in batches of ammo, or air density.

1858
March 21, 2010, 09:36 PM
From Wikipedia ....

The Coriolis effect is the behavior added by the Coriolis acceleration. The formula implies that the Coriolis acceleration is perpendicular both to the direction of the velocity of the moving mass and to the frame's rotation axis. So in particular:

* if the velocity is parallel to the rotation axis, the Coriolis acceleration is zero.
* if the velocity is straight inward to the axis, the acceleration is in the direction of local rotation.
* if the velocity is straight outward from the axis, the acceleration is against the direction of local rotation.
* if the velocity is in the direction of local rotation, the acceleration is outward from the axis.
* if the velocity is against the direction of local rotation, the acceleration is inward to the axis.

So in other words, make sure to shoot North or South so that you don't have to worry about it. The CF is at a maximum shooting East or West!! :D If your bullet has as a crappy BC, you may want to consider shooting East since your bullet will drop less!! :D

:)

BruceB
March 21, 2010, 09:55 PM
Take a hard look at the rear (barrel) sight on a M1903 Springfield.

The "rails" that guide and support the notch assembly when the sight leaf is raised are noticeably tapered, with the left side getting narrower as the range setting increases, and the right side getting progressively wider. This of course moves the sight element further and further to the left as the range setting increases. Does anyone here think that this was by accident? The arsenals knew full well that there is a ballistic factor that changes the impact point to the right as range increases.

Whether the change is caused by atmospheric effects or the Coriolis phenomenon, the fact remains that there IS a change. It's only obvious at extreme range, but it is there. To see a pretty good picture of the '03 sight leaf, go to www.auctionarms.com and search for item #9575909, and the tapered rails are VERY obvious.

According to my information, the British .303 rifles were rifled with a left-hand twist to compensate for the rotation of the Earth....in the NORTHERN hemisphere.

Dimis
March 21, 2010, 10:20 PM
i cants say anything for sure as im not a scientist a ballistition or anything more than a local rural boy playing with his toys but i believe the rotation of the earth only comes into play with extreme long range shots well beyond 1000 yards
like shots at 1 mile or beyond so for most of us it wouldnt effect us enough to notice or need to care
unless we are absolutly obsessed with absolute perfect accuracy which im almost possative is completly unatainable its a moot point

so unless you have a big boy rifle in a caliber that reaches 2000 yards and beyond its nothing to be concerned about

YMMV

Hud
March 21, 2010, 10:37 PM
It does have an effect, but...

From Canadian Manual:
B-GL-306-006/FP-001
FIELD ARTILLERY
VOLUME 6
BALLISTICS AND AMMUNITION

ďIn manual computations, rotational effects are not applied in Canadian gunnery procedures at ranges under 15000 metres, as the additional accuracy achieved does not justify the time expended.Ē

So, if they don't worry about it with artillery under 15,000 meters (that's 9 1/3 miles folks), I doubt if we need to be concerned with any calibers that we shoot at any range.

taliv
March 21, 2010, 10:46 PM
1) "they" == canadiens

2) sure, the additional accuracy might not justify an extra 20 minutes with a slide rule
but if it takes an iphone a second and a half to calculate it, why wouldn't you want the additional accuracy?

Hud
March 21, 2010, 11:34 PM
Well, I really donít feel a need for it, but if it works for you, Iím sure the iPhone app has it all over those stone-age Canadians.:)

benzy2
March 22, 2010, 12:24 AM
Take a hard look at the rear (barrel) sight on a M1903 Springfield.

The "rails" that guide and support the notch assembly when the sight leaf is raised are noticeably tapered, with the left side getting narrower as the range setting increases, and the right side getting progressively wider. This of course moves the sight element further and further to the left as the range setting increases. Does anyone here think that this was by accident? The arsenals knew full well that there is a ballistic factor that changes the impact point to the right as range increases.

Whether the change is caused by atmospheric effects or the Coriolis phenomenon, the fact remains that there IS a change. It's only obvious at extreme range, but it is there. To see a pretty good picture of the '03 sight leaf, go to www.auctionarms.com and search for item #9575909, and the tapered rails are VERY obvious.

According to my information, the British .303 rifles were rifled with a left-hand twist to compensate for the rotation of the Earth....in the NORTHERN hemisphere. Isn't the Coriolis effect one direction? Not just the farther out you shoot the further left you need to shoot? If you turn around 180* what was right to left is now left to right. I highly doubt the sights were designed only to face one direction, unless I don't understand how the Coriolis effect works.

Quentin
March 22, 2010, 12:57 AM
I think I'll quote myself from early on in the thread. Worry about the things that really are important. Most of us would be foolish to blame our misses on the rotation of the Earth!

...your gun and the target are lockstep, moving the same speed so I'd say forget about it and worry about what really matters like your shooting technique, breathing, ammo ballistics, the rifle/sights and weather conditions.

Art Eatman
March 22, 2010, 09:42 AM
benzy2, have you ever taken the center tube from a roll of paper towels and spun it to see the difference that direction in rotation makes? If you speedily roll it out from your hand so the top advances, it falls quickly. If the bottom advances in its rotation, it floats. IOW, the spin causes a pull to one side of the tube or the other, depending on the direction of rotation.

Now consider a bullet: Yes, it moves forward, but it's spinning. The spin causes a pull to the side. The angle of the ladder sight of the Springfield compensates for this pull.

CajunBass
March 22, 2010, 10:20 AM
I've always blamed it for me missing a dove once. ;)

Rollis R. Karvellis
March 22, 2010, 10:45 AM
Something else to keep in mind, the speed of the spin of the Earth is appox. 1040 MPH, at the equator, but the farther away from the equator you go the slower the spin speed is. Plus you might want to keep in mind that the higher in elivation you go the lighter your projectile will weigh. Let's not forget that the planet Jupiter can raise the Earth's oceans as high as the width of a human hair! Just think what that can do to the bullit. OR OR OR or we can just squeez the trigger' and enjoy the result.

taliv
March 22, 2010, 10:56 AM
yeah, benzy, like art said, i think the springfield sights are compensating for what's oft called 'spin drift', not the coriolis effect

Dimis
March 22, 2010, 02:35 PM
I think I'll quote myself from early on in the thread. Worry about the things that really are important. Most of us would be foolish to blame our misses on the rotation of the Earth!


haha this brings back memories of video games and "it was the controler not me" excuses

Kevin5098
March 22, 2010, 02:45 PM
What about relativistic effects?

Kentucky_Rifleman
March 22, 2010, 05:05 PM
What about relativistic effects?

Bah! Me pull trigger. Gun go "BANG." What in front of gun die. This good enough.

KR

benzy2
March 22, 2010, 05:38 PM
I get the spin drift idea. I thought we were claiming the sights were angled due to the spin of the earth, not the drift of the bullet due to its rotation.

Guns and more
March 22, 2010, 07:01 PM
That explains why my bullets have not been hitting the target dead center.
I feel better.

SpamHandler
March 22, 2010, 07:30 PM
benzy2, have you ever taken the center tube from a roll of paper towels and spun it to see the difference that direction in rotation makes? If you speedily roll it out from your hand so the top advances, it falls quickly. If the bottom advances in its rotation, it floats. IOW, the spin causes a pull to one side of the tube or the other, depending on the direction of rotation.


I believe this is the 'Magnus Effect'.

Quentin
March 22, 2010, 10:29 PM
What about relativistic effects?

We'll have to ask Albert about that! :D

Mandolin
March 22, 2010, 10:59 PM
So, if they don't worry about it with artillery under 15,000 meters (that's 9 1/3 miles folks), I doubt if we need to be concerned with any calibers that we shoot at any range.

"Close only counts wth horseshoes and 6" HE shells" Plus or minus a few feet dosn't realy matter when you're sending a 150lb hunk of high explosive downrange. Admitedly, a rifle round might be affected at very long range.

taliv
March 22, 2010, 11:17 PM
they didn't say they don't worry about it. they said that it wasn't worth the TIME it takes to MANUALLY CALCULATE it.

that's a perfectly reasonable statement.

maybe at the next big long range precision rifle tournament, somebody will make a stage where the competitors are given a pencil, calculator and a piece of paper with the formulas written. Let them shoot a couple close up targets, then make them calculate the coriolis effect, then take a final long range shot.

benEzra
March 22, 2010, 11:41 PM
What about relativistic effects?
It happens!

A 55-grain .223 at 3250 fps (20" barrel) is 3.56394 grams at 990.6 meters per second, for 1.748626 kJ of energy.

The relativistic Lorentz gamma for 990.6 meters per second is 1.000000000005459152744. So the bullet gains 1.94561e-11 grams of "relativistic mass" (19.4561 picograms). Or to put it another way, at the muzzle, your bullet has an effective mass of 55.0000000003 grains if it weighed exactly 55 grains at rest.

Somehow I doubt that's going to affect your trajectory, though...

unit91
March 22, 2010, 11:57 PM
I believe this is the 'Magnus Effect'.

We have a winner.

Oic0
March 23, 2010, 11:11 AM
What about relativistic effects?

That is exactly what causes it. Say you are firing straight south. You are spinning the same speed as the earth. Lets say that is 1500fps. Your bullet is traveling 1300fps to the side as it travels forward, the same speed as everything on the ground so no change. Then as the thing travels south it gets closer to the equator (and the surface is further form the axis, thus traveling faster to maintain the same rotation) and the ground is now going 1501fps in its sideways movement but the bullet is still going 1500. In that scenario the target is moving to the side a full foot for every second of flight time.

GMFWoodchuck
March 23, 2010, 11:26 AM
Don't worry about it. Until you own a 155MM piece it's not a problem.

Art Eatman
March 23, 2010, 11:26 AM
Magnus effect or any other name, a spinning cylindrical object will react to the aerodynamic forces created by its rotation. In my example, one direction of spin created a force to resist the force of gravity; the opposite direction of spin augmented it.

The direction of rotation creates a pressure differential between the sides, as viewed from the axis of spin. The behavior, then, is much like an airplane wing, with lower pressure on the high-speed, upper, side and higher pressure on the low-speed side. The differential creates lift forces on the wing--and pushes a bullet sideways.

Hud
March 23, 2010, 12:29 PM
Well thrill seekers, it seams we have covered all the things that can have an effect on our loooong range shooting except gyroscopic precession of a projectile, not the earth.

Driftertank
March 23, 2010, 01:37 PM
Correct me if I'm wrong, but doesn't the coriolis effect depend largely on lattitude? The British allegedly state that the effect is most pronounced when shooting to the southwest, does that mean the Austrailians would have the most trouble shooting northwest?

Now, for a real stupid hypothetical question, what would happen if one were to try for a 2-mile shot across the north pole? Would the Coriolis drift change directions? Or, since it's so near the axis, would the effect be minimal anyway?

I reckon I'll never even try for a shot past 1,000 yards. Even then, it would likely only be at the range. I consider my personal maximum effective range to be under 600 yards for a medium-game sized target, so this talk of Ultra-long-range ballistics serves only as an interesting theoretical excercise for me...

Hud
March 23, 2010, 01:40 PM
Chuck,
If you are refering to the Poisson Effect, it probably has less effect that the Magnus & anyway I thought I'd let everyone chew on precession for awhile.

Rollis R. Karvellis
March 23, 2010, 02:25 PM
What would happen in the 2 mile over the pole shot?

benEzra
March 23, 2010, 04:46 PM
Now, for a real stupid hypothetical question, what would happen if one were to try for a 2-mile shot across the north pole? Would the Coriolis drift change directions? Or, since it's so near the axis, would the effect be minimal anyway?
Assuming here that you're 1 mile from the pole and shooting at a target 1 mile on the other side of the pole, for 2 miles total.

At 1 mile from the pole, the gun is moving to the east at about 1/4 mile per hour as the earth spins (fast enough to complete the complete 6.28-mile revolution around the pole in 24 hours). The target on the other side of the pole is moving in the opposite direction at 1/4 mile per hour. That results in a 1/2 mile-per-hour speed differential between you and the target, and will result in a miss to the right if you are shooting at a small enough target. To hit it, you would have to lead it a little by aiming slightly to the left.

If you are 50 miles from the pole and shooting at a target 50 miles beyond, the gun is moving east at 13.1 mph and the target is moving in the opposite direction at 13.1 mph, for a speed difference of 26.2 mph. Bigger miss to the right.

Shooting over the South Pole, the miss would be to the left, not the right.

Note that in all cases, and neglecting wind drift, the bullet is moving in a straight line as the earth moves beneath it; the path only appears curved if you plot it on a map, or otherwise view it from a rotating rest frame.

One good way to understand the Coriolis effect is to take a friend and some tennis balls to a playground, get on opposite sides of a merry-go-round, spin it up really fast, and play a game of catch. From your rotating perspective, the ball's path will seem to curve in relation to you and your friend, although a stationary, nonrotating observer would see the ball moving in a straight line as you, your friend, and the merry-go-round spin around it as it flies.

natman
March 23, 2010, 04:59 PM
The Earths rotating and moving under the bullet is true.

Yes the bullet was moving at the same speed as the Earth, but not after it left the barrel.



Ok, what made the bullet stop moving the same speed as the Earth just because it is no longer in the barrel?

eye5600
March 23, 2010, 05:03 PM
What about relativistic effects?

In college physics, we did a lab with firing a .22 short into a ballistic pendulum in order to measure... I don't remember what. The prof did murmur something about the uncertainty principle for the bullets though it was not relevant to the experiment.

I was just bowled over by the college giving kids guns and bullets in the lab with not particular instruction or supervision. I suppose the experiment had been in use since the time when any and every kid in Maine knew about guns. And I suppose they don't do it anymore.

As for including the Coriolis effect in your ballistic program, I think it could make a difference of a quarter or half a bullet width at the target for a long range shooter, well worth the effort.

Dr. Tad Hussein Winslow
March 23, 2010, 05:22 PM
Ok, what made the bullet stop moving the same speed as the Earth just because it is no longer in the barrel?

Ahhh, good question. Nothing made it stop, but what made it *slowly slow down slightly, relatively speaking*, I believe, is the fact that it's no longer touching the ground, nor touching anythiog which is touching the ground, and therefore no longer being slightly nudged along by contact with the ground. Witness what happens when you shoo a fly our your car window, or jump high while standing on a rotating merry-go-round - you don't fall back to the exact same spot. Now it IS still nudged along somewhat by the air in the atmosphere which is matter that has mass and is also moving along with the earth - which is why a fly flying around inside your car does not fall back to the back window (the air mass inside the car is being pushed along by the interior extremities at the back of the car, pushing the whole air mass forward - but again, shoo it out the window and everything changes). But I think that in the air, the air cannot push the bullet along *quite* as much as being in contact with something which is in contact with the earth would push it along, so you get a small amount of coriolis. 'Course, I could be all wet on this. :)

You know, I think I AM full of it, because the 'earth spin' vector would not stop, due to the law of inertia, would it? ... not even in a vaccuum would that sideways vector & velocity change, let alone when also surrounded by an air mass which is moving along with the ground! Hmmmm - now I'm at a loss to understand the coriolis.... :(

Driftertank
March 23, 2010, 05:38 PM
Benezra, thanks. I think I knew that, but reading all this stuff confused the simplicity if the concept in my mind....

The easiest way, at least in my mind, to think about the Coriolis effect is to relate it to the Mythbusters episode where they debunked the bit in the movie "Wanted" about curving the bullet around an obstacle: no matter how fast you 'fling' the gun, as the bullet leaves the barrel it assumes a straight velocity vector. While it is effected by air resistance and gravity, movement of the barrel does not induce a progressive vector change after the bullet leaves it: the bullet travels, in a straight line, in the direction it was travelling at the moment it left the barrel. For the same reason, the shooter, moving along an arc as he would be on the surface of the earth, doesn't impart the movement of the earth's arc into the bullet after it leaves the barrel; it continues to travel in a straight line (barring wind changes). The earth rotates under it, inducing a RELATIVE change in the bullet's vector, which is minor, but over the tame lapsed from firing to impact on a very long-ranged shot, can noticeably change the bullet's impact point.

But the biggest influence, aside from the shooter's movement, which changes POI, is aerodynamics...manifesting in both windage and spindrift. Gravity falls right behind it, as the shot's elevation has a marked effect on POI as well. Unless you're making REALLY long shots, the coriolis effect is negligable as an influence on POI.

rcmodel
March 23, 2010, 05:44 PM
What happens when the wind is blowing 20 MPH, 180 degrees opposite the direction of the earths rotation?
Or if the wind changes and blows 180 degrees the other way, it is still a 20 MPH wind.
And you are shooting 90 degrees north or south too it?

You still have a 20 MPH crosswind to contend with when shooting long range.
You have to allow for that wind, but you don't have to allow for the earths rotation.

rc

taliv
March 23, 2010, 05:55 PM
the most important part is if you're shooting straight up with no wind. someone should calculate whether the coriolis effect would be enough to cause it to miss the shooter

Driftertank
March 23, 2010, 06:02 PM
Depends on the type of round. Most rounds have sufficient flight time to make the answer yes, but in the real world, wind makes much more difference.

Mythbusters did another episode where they fired several guns straight up. Their rounds landed all over the place.

benEzra
March 23, 2010, 07:21 PM
What happens when the wind is blowing 20 MPH, 180 degrees opposite the direction of the earths rotation?
Or if the wind changes and blows 180 degrees the other way, it is still a 20 MPH wind.
And you are shooting 90 degrees north or south too it?

You still have a 20 MPH crosswind to contend with when shooting long range.
You have to allow for that wind, but you don't have to allow for the earths rotation.
Wind effects do dominate, yes. Coriolis only comes into play when you're using really heavy projectiles, shooting at really long ranges (many miles), and/or punching rounds into the stratosphere. Think "long range artillery".

Of course, with modern guided munitions, Coriolis inertial effects are almost as irrelevant to projectiles as they are to airplanes and cars; if the projectile is actively steering itself where it is supposed to go, the initial trajectory only has to be approximate.

SpamHandler
March 23, 2010, 08:58 PM
Art, I was just showing that your example was not of the Coriolis effect, but of another effect acting on the projectile. (Very illustrustrative example that you provided, BTW).

The direction of rotation creates a pressure differential between the sides, as viewed from the axis of spin. The behavior, then, is much like an airplane wing, with lower pressure on the high-speed, upper, side and higher pressure on the low-speed side. The differential creates lift forces on the wing--and pushes a bullet sideways.

The lift created by a wing is due to the Bernoulli effect, and relies on air following a longer path along the upper surface to lower the pressure above. Since a bullet doesn't have such an irregular surface, being a circle in cross-section, it is much more dependent upon the wind velocity to effect any change in lift or drop. The pressure differential is responsible for both.....but due to 2 different effects.

Ohio Gun Guy
March 23, 2010, 09:09 PM
I'm jumping in late here and only read the last few posts.... I'm not convinced.

Not for small caliber. MAYBE for a .50 cal fired at a VERY long range. Wouldnt the bullet have to be free from the earth for enough time for the earth to essentially spin under it? I would think that since the atmosphere is rotating also, at nearly the same speed this effect, if any, would be minimal and only have effect on shots that have a much longer flight time than most small arms.

However, I may use this as an excuse next time at the range.....:evil:

hogshead
March 23, 2010, 09:35 PM
Didnt you guys watch shooter, Mark Walberg said you had to take into account the rotation of the earth. Came from Hollywood and I know they know. Obtw I'm just a peckerwood with to many guns too.

Quentin
March 24, 2010, 01:12 AM
I wonder just how much Mark Walberg and the Hollywood crowd know about rifles. :neener: Less than we do, that's for sure!

scythefwd
March 24, 2010, 01:57 AM
I have only heard of this mentioned once by long range shooters that happen to be friends. One is on the Army shooting team, he doesn't care. One was a scout sniper, and as long as he isn't traveling he doesn't care. The scout said that it only became a consideration when he was drastically changing latitudes and taking long shots. Since he still practices at 600-1k yards (or is it meters) I would be interested in what he considers long shots.

I take it that if you sighted in in Gnome, Alaska, and are sent on a sniping mission in Brazil it would matter. You don't get a ton of shots to sight in and adjust your POI vs POA when you are trying to sneak in without being noticed. If you have all day to sight in I wouldn't bother with considering it for small arms.

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