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 November 25, 2012, 05:36 PM #26 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 6,318 I use a Dwyer wind gauge to read the wind speed at the firing line. Cheap and accurate. Then use a constant for the bullet and its muzzle velocity to calculate corrections based on wind speed and directions. Here's a table showing the wind speeds above the line of sight: If you look at the trajectory path of a bullet, it spends only about 25% of its time at the top of its arc where wind speed's the fastest. 50% of its time in the middle wind speed range and about 25% in the lowest speed range. The following's a table showing how much the wind has at different ranges for a given crosswind across the entire trajectory:
 November 25, 2012, 06:54 PM #27 1stmar Senior Member   Join Date: March 21, 2012 Location: Connecticut Posts: 2,096 Thanks guys, really appreciate the education on this.
 November 25, 2012, 08:25 PM #28 tobnpr Senior Member   Join Date: August 1, 2010 Location: Tampa Bay Posts: 4,332 The range we frequent (finally) put flags at 100 yard intervals all the way downrange. This has served to frustrate and confuse even more, because now we KNOW what we used to only suspect- that the wind is doing something completely different at every flag (and no doubt, in between as well). I have no doubt that shooting on an open plain or a range that's not surrounded on all sides by twenty-foot tall berms would be much simpler. Even a 5 mph wind swirling inside a punchbowl is going to be challenging. Bottom line, it's all fun to talk about theory, but just get out and send 100 rounds as often as you can- and try to learn from the frustration. This is where a good brake- if you don't have a spotter- is indispensable. It's more important to spot your misses, than your hits....or it's just a waste of expensive ammo. Pay attention to the conditions when you break the trigger- make your adjustments and keep good notes.
 November 26, 2012, 10:45 AM #29 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 6,318 Using a spotting scope to read (see) the mirage (heat waves); lesson 1: Get a 20X to 25X spotting scope, mount it on a tripod so it's very steady. (NOTE; you can also use a rifle scope of at least 15X that has an adjustable objective so you can focus it at some distant range.) Go outside on a warm day when the wind's blowing a little bit (no hurricanes at all) to someplace where you can see at least half a mile over reasonably flat ground. Point the scope at something about half a mile away, then focus it so the image is as sharp as you can get it as you see it. Note the direction the wind is blowing; left to right or the reverse thereof. Look through your spotting scope at the thing you focused on then change focus to something closer; move the focus adjustment very slowly. As you change focus to something closer you should see the wrinkling heat waves (mirage) become clearer and easier to see as they look like running water moving across the scope's field of view. It's the wrinkle close to and just above what your looking at that counts the most. Move focus as close to where your are as possible so you can see how the mirage appearances changes with focus. Sit down, take a break then do this over again. What happens is as the light rays from the far away things go through the air to your eyes, their direction gets changed by the air temperature in it and how its moved around by the cross wind. Find a focus point where you can see the mirage clearly then watch it speed up as the wind speed increases or slow down as the wind drops. Watching the mirage (reading the wind in competitive shooting language) will let you know whether to move your sights into the wind if it speeds up or away from it if it slows down. Doing this keeps your shots falling at the same place. How much to move your sights for a given visible wind change? That's lesson two. Last edited by Bart B.; November 26, 2012 at 10:58 AM.
 November 26, 2012, 11:30 AM #30 mapsjanhere Senior Member   Join Date: August 6, 2009 Location: Albuquerque Posts: 2,774 I disagree on the "reaiming" by a short burst of air close to the muzzle being worse than the same burst close to the target. As long as your bullet is well stabilized, it stays on it's original track, and only gets pushed sideways for a given time. The only difference would be due to the differential speed at muzzle and at target, and that effect is contrary to the one described, close to the target the bullet is slower and would be affected more by as side wind. __________________ I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.
 November 26, 2012, 01:24 PM #31 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 6,318 What is "reaiming?" Never heard of that term. Do you think a bullet that's been pushed sideways by a cross wind blowing to the left, then that wind stops, that bullet will make a right turn back to parallel to its path before the wind moved it and strike the down range target a distance equal to its position left of the line of sight when the wind stopped? Last edited by Bart B.; November 26, 2012 at 04:23 PM.
November 26, 2012, 01:38 PM   #32
kraigwy
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Quote:
 I disagree on the "reaiming" by a short burst of air close to the muzzle being worse than the same burst close to the target. As long as your bullet is well stabilized, it stays on it's original track, and only gets pushed sideways for a given time. The only difference would be due to the differential speed at muzzle and at target, and that effect is contrary to the one described, close to the target the bullet is slower and would be affected more by as side wind.
Now I'm really confused. Wish I hadn't read that.
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 November 26, 2012, 04:26 PM #33 Erno86 Senior Member   Join Date: September 22, 2012 Location: Marriottsville, Maryland Posts: 1,287 Picher's #22 post...is probably correct for a firearm with a right hand twist --- for a left hand twist, the vertical direction would be opposite. I'm not a expert on the subject of wind deflection, so if I make any mistakes --- please correct me. Wind deflection is based on a arc. A bullet...that is affected by the wind as it first leaves the muzzle, will have a greater horizontal arc deflection on the bullet, than a bullet that is affected by a wind downrange. At very long distances...wind will have a much greater horizontal arc deflection effect on bullets downrange; as the bullet slows down. Besides wind flags, mirages, wind meters, wavy trees and flying leaves --- I'am trying {for 22 rimfire} to dope the wind speed and direction...by the way the wind hits my face or neck --- in a way that I can determine wind speed and direction, so I can instantly correct holdover's --- a steady wind helps. David Tubb... has an excellent book on wind deflection --- along with other shooting accuracy tips. Tubb...focuses his spotting scope, ten yards short of the target --- so he can read wind mirages. Last edited by Erno86; November 26, 2012 at 04:56 PM.
November 26, 2012, 06:05 PM   #34
Bart B.
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Erno86 mentions:
Quote:
 David Tubb... has an excellent book on wind deflection --- along with other shooting accuracy tips. Tubb...focuses his spotting scope, ten yards short of the target --- so he can read wind mirages.
I doubt that. I don't know of anyone who can resolve focus good enough to discriminate between a perfect focus on two things 10 yards apart at 1000 yards. Even with a spotting scope with a 100 mm diameter spotting scope objective lens. I've tried it with the finest optics on this planet and with near 20-10 vision most of my life, could not resolve focus between two things 10 yards apart at 1000 yards.

I'm surprised if David really put that in print. Well, kind of surprised. Having known David since he was a teenager back in the 1970's and shot many a match with him and his dad, George, David's well known in High Power Rifle competition as one who "stretches" things to gain an advantage. I've watched him adjust focus on his spotting scope every time he gets ready to shoot. If he really did focus at the same place all the time, he would not have to change focus on his spotting scope.

Most match rifle competitors focus their scope somewhere between them and the targets range so they can see it wrinkling across their field of view centered just above the target image. You need to see that mirage wherever its at. Shooting 5 days in a row on the same shooting range at targets from 200 to 1000 yards away, I've noticed I have to change focus for each target distance depending on which direction the winds come from as they ain't uniform across the low hills and valleys around the range. Whatever focus gets you the best mirage is what you use. It can also change from time to time during the day.

Last edited by Bart B.; November 26, 2012 at 06:18 PM.

 November 26, 2012, 06:50 PM #35 mapsjanhere Senior Member   Join Date: August 6, 2009 Location: Albuquerque Posts: 2,774 My post was in response in to BLE's #11. And yes, the bullet will continue parallel to it's original path. Otherwise you wouldn't get the linear deflection for constant wind. If the bullet would change direction, the deflection would be exponentially increasing with distance (which everyone agrees it is not). __________________ I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.
November 26, 2012, 08:00 PM   #36
B.L.E.
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Quote:
 My post was in response in to BLE's #11. And yes, the bullet will continue parallel to it's original path. Otherwise you wouldn't get the linear deflection for constant wind. If the bullet would change direction, the deflection would be exponentially increasing with distance (which everyone agrees it is not).
Actually, wind drift is exponential with distance in a constant wind.

Here's the calculation of a standard velocity .22 long rifle bullet in a 10 mph cross wind.

25 yards 0.3 inches
50 yards 1.3 inches
100 yards 5.1 inches
200 yards 19 inches

It's linear to wind strength, exponential to distance.

November 26, 2012, 08:46 PM   #37
Bart B.
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B.L.E.'s astute observation:
Quote:
 Actually, wind drift is exponential with distance in a constant wind.
Correct.

Another way to grasp this reality is that bullet moves sideways with the wind at the same rate from muzzle to target in a constant crosswind. For each tenth of a second it goes down range it will travel a shorter distance. So, for each tenth of a second it goes down range the more its trajectory curves to the side.

 November 26, 2012, 08:59 PM #38 tobnpr Senior Member   Join Date: August 1, 2010 Location: Tampa Bay Posts: 4,332
 November 26, 2012, 09:18 PM #39 B.L.E. Senior Member   Join Date: December 20, 2008 Location: Somewhere on the Southern shore of Lake Travis, TX Posts: 2,447 Furthermore, if the bullet hits a gust of wind at 25 yards and there is dead calm the rest of the way to the target, the bullet will continue on its new path and get further and further away from the original path, just as if it had been deflected by a twig or blade of grass. If it hits a left gust at 25 yards, and then a right gust at 50 yards, now it will fly roughly parallel to its original path but displaced sideways a little.
 November 26, 2012, 10:34 PM #40 TXAZ Senior Member   Join Date: September 5, 2010 Location: Cyber-Texas Posts: 2,688 Linearized not linear So I'll throw in the Physics spoiler, and a way to maximize the hit potential in the future: Virtually none of the variables or factors that are generally considered in ballistics calculations are linear when it comes to turbulent or laminar flow. The charts that are used are subset of multi-ordered (like 5th to 9th order) differential equations (the bane of even hard core engineers). A Psychometric chart (like to one at Wikipedia here http://en.wikipedia.org/wiki/File:Ps...eaLevel.SI.svg ) is pretty simple in relationship to predicting the precise location of a projectile at 500 meters. I only mention this as if you start to interpolate some of the numbers outside their current range (ie "if it works at 300 yards then 600 yards must be twice / half the value"). If you want to take the easy route out, look for laser guided projectiles in the near future. DARPA has developed a pretty sophisticated device. Expect to see significantly lower cost guided bullets that are more like laser guided bombs often called 'bang bang' guidance systems, that require the laser illumination to be within a few degrees of the flight path. Either can can hit the left or the right nostril of a deer at 1000 yards 90% of the time. Ain't math wonderful? __________________ أنا لست ارهابيا .50 BMG: 1 Shot 1 THRILL!
 November 27, 2012, 07:50 AM #41 Picher Senior Member   Join Date: December 14, 2004 Location: Maine Posts: 3,321 Subsonic bullets are affected vertically by air friction against the rifling marks to a much greater extent than supersonic bullets, which have a shock wave that minimizes air flow along the parallel body of the bullet and the "fins" created from rifling. Exception: Bullets, like barely supersonic .22LR high speed bullets that, as they slow down between muzzle and target, pass through the supersonic>subsonic transition zone, which causes them to deflect horizontally about 1/3 more than bullets that either stay supersonic, or start as subsonic rounds.
 November 27, 2012, 09:42 AM #42 Jimro Senior Member   Join Date: October 18, 2006 Posts: 7,089 Actually it is exponential to wind because as you change the path of the bullet you are changing the distance. Imagine shooting into a wind so strong you had to aim 45 degrees off line of sight to get your bullet to the target, as you can see, the bullet now has to travel a much longer path and it would in a no wind condition. As the bullet path distance increases, corrections have to get larger and larger for each correction, something you would expect from an exponential (or trigonometric) function. For small wind values, 20mph or less, obviously a linear approximation is accurate enough. But don't confuse a linear approximation of an exponential for linearity. Jimro __________________ Machine guns are awesome until you have to carry one.
November 27, 2012, 10:13 AM   #43
Wyoredman
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Quote:
 Were in the hell do you guys shoot were the wind blows at the same speed and direction all the way to the target?]
Guess you have never shot in Wyoming!

A better question would be "Were in the hell do you guys shoot were the wind only blows 5-10 mph?"
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 November 27, 2012, 11:01 AM #44 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 6,318 Madcratebuilder asked were in the hell do you guys shoot were the wind blows at the same speed and direction all the way to the target. There's four rifle ranges I've shot at where the winds under 5 mph are very consistant in speed and direction and the terrain's very flat: Camp Perry, Ohio, Viale Range on the 1000 yard line when the wind's from the northeast coming in from Lake Erie. Puuloa Rifle Range at Ewa Beach west of Honolulu, HI, at what's now a Naval Magazine area when the wind's from the southwest. Colorado Rifle Club range about 10 miles north of Byers, CO when the wind's from the east. Sho-Bon Rifle Range east of Shoshoni, WY, that's no longer there. Any wind from the south was very consistant across its 1000 yard range. There's lots of antelope hunting areas in the flatlands of northeast Colorado as well as south east Wyoming where this happens. Last edited by Bart B.; November 27, 2012 at 11:16 AM.
 November 27, 2012, 11:26 AM #45 Wyoredman Senior Member   Join Date: September 6, 2011 Location: Wyoming Posts: 1,320 I was hunting coyotes last weekend between Shoshoni and Casper. The wind was from the west at a constant 30 mph. I couldn't hit anything with my .204 with those 32 gr Hornadys! Should have brought my .30-06, I might have connected on a few! Reading wind drift seems more of an art than a science, to me. __________________ Go Pokes! Go Rams!
 November 27, 2012, 12:37 PM #46 Bart B. Senior Member   Join Date: February 15, 2009 Posts: 6,318 Best guessing for a wind correction I've seen was at the 1988 World Long Range Palma Matches in Sydney, Australia. Practice day before the matches started had mild winds in spite of the range being 200 yards away from the beach. On the day of the big team match, the wind Gods had turned on their after burners. I measured wind speed from 8 o'clock on the range at the 800 yard line on my gauge at 30 to 35 mph. All four US team line coaches as well as the head coach felt the first sighter should be made with 29 minutes of left wind so we all went 116 clicks left for openers. That pointed the barrel over 24 feet to the left of the target when our sights were on the bullseye. I and one other guy on the first relay shot first and our shots were about 3 seconds apart; mine struck the 4 ring on the left side, his the 4 ring on the right side. Both missed dead center in the 5 ring by about 20 inches. Such is life when the wind gusts as I fired and his bullet caught more of it than mine did.
 November 27, 2012, 04:00 PM #47 Erno86 Senior Member   Join Date: September 22, 2012 Location: Marriottsville, Maryland Posts: 1,287 Bart B. --- If I misquoted David Tubb...I want to make my apologies to David Tubb. No doubting, what you said is true ---that is --- hunting for mirages with your spotting scope at 1,000 yards. You can tell...I'm a novice, in long range shooting sports --- for the furthest I've shot --- is 200 yards, at the AGC gun range located on Marriottsville Rd, in Baltimore County, Maryland. Thanks for the input. Cheers, Erno86
November 28, 2012, 09:48 AM   #48
madcratebuilder
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Quote:
 Madcratebuilder asked were in the hell do you guys shoot were the wind blows at the same speed and direction all the way to the target. There's four rifle ranges I've shot at where the winds under 5 mph are very consistant in speed and direction and the terrain's very flat: Camp Perry, Ohio, Viale Range on the 1000 yard line when the wind's from the northeast coming in from Lake Erie. Puuloa Rifle Range at Ewa Beach west of Honolulu, HI, at what's now a Naval Magazine area when the wind's from the southwest. Colorado Rifle Club range about 10 miles north of Byers, CO when the wind's from the east. Sho-Bon Rifle Range east of Shoshoni, WY, that's no longer there. Any wind from the south was very consistant across its 1000 yard range. There's lots of antelope hunting areas in the flatlands of northeast Colorado as well as south east Wyoming where this happens.
There are exceptions to everything, but most ranges are build facing hill sides or have breams for safety. The majority on my long range shooting done hillside to hillside on blm land. Occasionally I well cross the mountains to the flat scrub lands. You well seldom have the same conditions from the firing line to the target.

 November 28, 2012, 01:36 PM #49 kraigwy Senior Member   Join Date: June 16, 2008 Location: Wyoming Posts: 10,822 It gets drafty at 29 Palms. I shot a service rifle (M1A/308s) 1000 yard match one year in some wind that woud make Wyoming proud. Took me a bit to get on, but when I did I was shooting lots of right wind and aiming at the neighbor's target. Had a good string going until..... The range officer told the line, to notify the pits if you finished or quit shooting so they can pull the targets to keep the wind from tearing them uo. As I said I was doing good, then someone pulled target. I call to have my target put back up and my scorer says, "Your Target is Up". I had to start all over, lost quite a few points. It's all fun. __________________ Kraig Stuart CPT USAR Ret USAMU Sniper School Oct '78 Distinguished Rifle Badge 1071
 November 28, 2012, 07:37 PM #50 old roper Senior Member   Join Date: June 11, 2007 Posts: 1,487 kraigwy, I spend little time at 29 Palms and I spend about 2yr working at the Wheatland Power Plant then almost yr at Ft Warren the few project from Laramie to Rock Springs and you guys have wind. We have wind here in Co but nothing like you guys. Don't mean to disagree with you __________________ Semper Fi Vietnam 1965 VFW Life member NRA Life Member

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