Long Range 101 Part 32 - Wind Corrections (2/2) - Rex Reviews 

Come train with Rex - in person!!! rexdefense.com/

Two 40 minute videos with diagrams, concise explainations, examples and pictures = "Real brief crash course" in windage haha oh man, love this guy.

Woah. I'll have to watch this one a few more times.

Rex, I must say like many others that I do enjoy your videos, as I am at KAF and will be for the next few months, you keep me from going crazy. Just wanted to say thank you.

by far the best gun related channel on RU-vid.

Rex you da man, you’ve got this all laid out step by step. Kinda like chemistry but nowhere near as hard lol.

Great question. We will assign cosine values in two ways: Vertical angle of fire corrections and lateral crosswind value determination. It really a matter of how we choose to describe our angular components. For determining actual horizontal range, we assign the full cosine value of 1.0 (100%) for level ground (0 degrees slope), which makes sense. For our crosswind values, a full value of 1.0 (100%) will be assigned to a direct crosswind (commonly designated as a 90 deg wind).

Holy crap, here I thought you could just take pot shots from a kilometer away but it takes enormous amount of effort to make those shots. Incredible amount of information.

I had made notes this summer for shooting my .22 out to 400 yds. Two days ago I almost threw them away because I needed three additional mills elevation and way more windage than before, up to 4-5 mills in a light breeze. Only difference is it was about 8F. You just cleared up a lot of confusion for me Rex. Working on getting my Rem 700 .308 with a SWFA SS 10 x together now. Should be a lot of fun! Thanks for the awesome vids.

Mirage? Yup, sounds French to me. I will do an entire video on long range spotting, which will go into more detail into this topic. Yeah, its all snowy here as well. Its been well below freezing for a long time.

Awesome video series man. I have downloaded them all so far so I can watch anytime without connection to the internet. Really appericate you taking your time and giving great explanations on long range shooting. Really helps clear things up Im sure for the most of us. Great music also by the way. Please keep them coming!

This stuff is kind of intimidating. Really setting me in my thoughts of not shooting at game at ranges more than 500 yards

Love the physics involved

Rex, you have a lot of students. Thank you for your video courses and sharing them with us. I am doing much better with my shooting today as a result of your videos. Soon, we will need student IDs!

Not usually, if we are doing everything else correctly. Most guys who adjust the BC are trying to get their drop data to match the "impact reality". Usually the difference between the calculated drop data and impact reality is due to unexpected and undetected muzzle velocity variation (MVV). Many shooters chrony a given load a few times and mistakenly assume the average MV stays constant. However MVV due to numerous factors is usually the culprit and not the BC.

Thank you, sir. The angle of fire episode should be pretty interesting for sure.

Rex, excellent videos. The .308 shows your point well. This is why I shoot a 7mm with a G1 .614 BC. These corrections are cut in half for wind drift. i will never know why a .308 bullet is used under 190g. Choosing a bullet with a high BC is half the battle

Rex, for clarification, the Cos function as you illustrated will yield your y-axis deflection, or head/tail wind component, except in the case of 45 deg where the Sin and Cos functions are equal. Cos of 0 is 1; Sin of 0 is zero. As such, for the x-axis deflection, or cross wind component, apply the Sin function to the illustrated angle.

Good question. the problem is that the wind never really goes on any exact angle, its always changing - so you will have to make your best estimation using a protractor or a clock sheet you make up with the angles illustrated.

lol - I know the dilemma. The truth is any of these stocks will work fine. My buddy has a real affordable aluminum bedded Choate target stock on his custom Surgeon 6mm BR and it shoots awesome. However, I would recommend getting the stock you "always wanted" right away. If you don't, you will always wish you would have, and then you'll end up buying it later anyways, then you'll have two stocks and you'll have to but a new rifle for the old one.......Any of these stock will work great :-)

Thank goodness for apps like Strelock Pro. It does all this math for you and takes wind angles, temps and everything into consideration. But knowing why is also important.

You got it, bud. Much more to come.

The max ordinate will in fact occur very very close to the halfway point of the TOF, however its not at the slowest velocity of the bullet. The slowest total velocity will be at the terminus, not the max ordinate.

No problem, sir. That would do it for sure. Cold air is a bit more dense than warm air.

Hi Rex! I'm new to shooting. Just bought a .22 rifle to start off. Its a savage bolt action. I'm really interested in getting into competitive shooting as well as hunting. Can I apply the same methods described in your videos just obviously accounting for short range and lower caliber? I bought the gun to hunt rabbits but your videos have inspired me to learn to SHOOT! Thank you for your inspiration. Your knowledge is truly to be admired! Thank you in advance... Alan

Very enlightening. I like the technical / scientific details you provide; much appreciated. Hi Randy! (Just checking if my friend is tuning in)...

thank you very much for sharing your time and knowledge!

Right now, just find a load that is accurate - after you establish a load that shoots well you will start your logging. Primarily your muzzle velocities @ different ammunition temperatures and also @ different bore conditions (clean vs thoroughly coppered, old vs new). MV log should have these 4 columns: Measured MV / Ammo Temperature, chamber temperature / state of bore The more MV data you get over varying conditions, the better your charts will be when we put them together.

I was having to use sine not cosine to get crosswind values. Cosine worked great for actual horizontal surfaces

I have a pretty serious question regarding this. I didn't recall hearing anything on it.. let's say you have the wind readings at the shooting position, at the target, in between and even the change of wind at the different elevations. As the bullets velocity slows down as it approaches the target won't the wind effect it more as the bullets gets closer to the target? This would be some sort of quadratic equation I think.

You can skip the scientific calculator and use the clock image to figure out the percentage adjustments for elevation and windage by separating the vectors on your clock: in your shooting log have a circle with a crosshair through the center, put a gradient from 0 to 100 out from center to perimeter of the circle, draw line from center to where wind is coming from, draw lines from where wind direction touches circle horizontally until it touches elevation line and vertically until it touches windage line, read the percentage where the lines intersect and apply your correction.

a + b = c ???? Sorry man, you will have to tell me which exact formula you are looking for... To properly adjust for wind, you will have to know how to APPLY the different formulas correctly. I could give you the formula e=mc2, but you would have no idea how to get anything out off it w/o understanding nuclear physics. This shooting discipline requires patience and strict attention to all the details. Mastery of all the concepts is required for serious LR shooting.

Mind blown again.... Keep up the good work

Jacob, The difference is that your calculator is assuming you're in Radians (another unit for measuring angles). Go into the options and switch your angle unit to degrees, and you'll get the .707.

Just watched your visit to the indoor rifle range in Switzerland. I couldn't help but think about the the absence of wind along with constant ambient temperature and the exact known distance of 300 meters. Never did figure out the target situation -- did you get your paper targets? It seemed like all you got was an image on a representation on a monochrome display.

The angle from the line of sight to the direction of any ordinate would = arctan (perpendicular height from line of sight to ordinate / ordinate distance from you along line of sight) The angle should then be converted from the calculator's setting of degrees or radians to the scope's units of MOA or mrad. In your case, ordinate distance along LOS could = .60 * 1 mile. This is coming from my knowledge of trig cause I've never shot farther than 200 yds, so see what approach others take as well.

Idea, instead of using max ordinate as you have no way to measure height anyway use the come up. If the scope is set 10 mil up, then so is the bore and thus the angle of the trajectory. So if using a spotting scope with a reticle or rifle scope to see mirage. Use that reticle to look 10 mil up from the target and that should indicate the top edge of the trajectory.

A mathematical way of finding the actual height at the max ordinate instead of estimating, for example 50 meters in the air at 500 meters (not realistic i know just making the point) is to use that scientific calculator and find the Tangent angle from your FFP. I mount an angle indicator on the spotting scope and after a quick calculation i move it to the tangent angle and now i am exactly pointed at the max ordinate. T = 50/500, T=0.1. now use the tan -1 button and u get 5.71 degrees.

First, thankyou for this series. Very helpful and interesting. One small thing i did note. You said a headwind increases the drag on the bullet. This is technically incorrect from an aerodynamics view isn't it? The bullet will be travelling at the same velocity through the air mass with a specific drag. If there is a head wind the drag will be the same as through the still air - it has the same velocity. The groundspeed however will differ. I guess you could say the value of drag would differ at the terminus however as the bullet has had to travel through a larger mass of air. Wouldn't the parasite decrease due to the decrease velocity? Any feedback would be appreciated!

Thank you! I will have to look for this "moirage" (or whatever it's spelled; seems like french word ;) ) through a telephoto lens. Hopefully the sun comes and visits us soon, we only have snow here at the moment :( Great video as usual!

so kinda think of air as water, I mean it's fluid dynamics, it's why profile of a ship's hull is so much like a profile of the bullet

Sorry I just have a quick question if you are trying to add all three wind speeds up, but in these three locations there are all different wind directions. Therefore, in this case, how do you add all three wind speeds up? Like if you want crank you turret how do you do?

Another great video Rex. Question: the peak of the trajectory is the halfway point of time of flight and the slowest velocity of the bullet, right?

Rex,Between part 1 and part 2 of your wind correction videos I saw a video on Accuracy 1st's Whiz Wheel. I like that it was an analog solver and that it solved a number of variables. When it came to the wind correction it showed a clock but said the correction is solved using cosines. I was wondering if you've seen/used that device and what your thoughts were? While surfing the web I also found and printed out a pilots Density Altitude Chart which was pretty interesting.

Hi,Really enjoy the series you've done. It has greatly help improved my overall shooting skill. I just have a quick question to see if I've not got this wrong, but in this episode at time index 14.32 min on the section on 10mph tail winds.You state that the 90F shot would impact just above the shoulder with the 60F shot landing above that, followed by the 30F shot landing higher than the 60F shot. Shouldn't this be the other way round as the 90F load is leaving the barrel faster due to internal ballistic & encountering less drag through the air with the tail wind & lower air density. So the impact point for the 90F shot should be at the top above the 60F shot with the 30F load at the bottom?

Hey Rex. I want to thank your for your video series on shooting long distance. I have a question regarding temperature correction for traverse adjustment. You talk about internal ballistics and muzzle velocity. My question is this, "For long range shooting, is the BC ever corrected for temperature, and if so, where would this take place?"

Actually for wind you want to use angle sine for the windage adjustments. Angle cosine would be the head component of the wind (elevation adjustment). Your example in the video happens to be correct because cos(45) = sin(45).

According to your wind angles at 21:30, if you run the cosine on those numbers you would be getting .924 from your 22.5 degrees that you have drawn by your zero value head wind and tail wind; and, you would have .383(rounded up) at your 67.5 degree line. These should be flipped, otherwise your correction value is increasing as you get further away from your full value. You would want your line of fire to be 90 and your full value wind to be 0. This would make your cosine for a full value wind to be 1, Deviating from that by 22.5 degrees would give you .924 of full value, deviating to 45 degrees would be .707, going further to 67.5 degrees would give you .383 and then going to 90 degrees(line of fire) would give you 0. In short: you want to use the sine of the angle of wind relative to line of fire, not cosine.

good stuff, rex. keep em coming.

Hi rex during the video you show a table with angle of fire cosines and wind cosines why are the values for each angle different on each chart ?

Very good video REX! How do you calculate the effect of a headwind in the trajectory???

Rex, at about 16:30 you are talking about a quartering wind from approximately your 7 o'clock. In the caption of the muley you have a 0.45 moa Up correction, should that not be down since there's a tailwind?

Ye Gods, those Kentuckians must have been freakin geniuses.

first, great videos and a ton of information. Thank you for all the effort. At 18:41, the protractor method, the values for hold off using COS are great for the 45 degree wind gradient. 70% of the value. If you use the remainder of that quadrant to calculate the hold off value, 22.5 and 67.5 degrees respectively, the values would be .92 and .38 leading one to believe that at 22.5% you use 98% of the hold off. If you switch these two values on the clock diagram, meaning measuring from 90 degree's and not from 0 degrees, the value of hold off would be to use 38% (COS 67.5=.38) with wind from the 1:30 or 67.5 degrees up from 90 and 92% from the 22.5 degrees up from 90 degree wind. assume this would be close for a tailwind as well. Am I on the right track with this thinking?

I'm sorry. Trashcanistan is not exactly the world's most lovely vacation spot, and KAF not the highlight of it either... Good time to catch up on your studies! Be safe, you'll be home before you know it :-)

All those variations in the wind must be extremely difficult to account for. The main wind is one thing, but with the convection and all it sounds almost impossible =/ Take the mountain/valley picture you showed for example. Its actually the sun that heats up the cliffs (sunny side) that through convection heats up the air and makes the air rises, that makes the wind sort of going upp the hills. It doesnt act like this in shade (so if you have a valley with one hillside in sun and another in shade, they will act differently). And since the big masses of warm air, when they let go of the terrain (thermals) doesnt do that cinsistently but rather in big chunks, the anabatic wind (wind that goes up the hillside) is not constant at all. A nice sunny day with NO headwind what so ever, can still have anabatic winds upp to 30 kph or more coming in forceful gusts. And when you think of that all the air that is rising is in need of new air to fill its place, you wil have sometimes VERY strong valley winds aswell. And to account for all this variables along side the different temperatures in airmasses, I think I will have nightmares about this for along time =//

In part one, when discussing the formula with the constant such as 15 for 100-500m, 12 for 900m, etc., you mentioned that the order of operations was important. No, it makes no difference. You can divide the range in 100's by the constant, and then multiply that by the wind speed. In the example given, you 9 multiplied times 8 first, then divided by 12, which gave you 72 / 12 = 6. You could have just as well have divided the 9 by 12 first, and then multiplied it by 8, as in 9/12=0.75, and then 0.75x8 = 6.

hey Rex, thanks for the videos man, l just want to ask you from where you get your wind correction charts that you used in your videos? thanks again.

Hello Rex. Thanks for all the information and wonderful videos. I have a question. All these calculations are based on a 10 mph wind, from which we take the angle cosine and apply that value off our ballistics chart's data. How do we calculate the value for other wind speeds? Our ballistics charts are based on a 10 mph, 90 degree cross wind. What about other wind speeds? For example, a 12 mph wind. Or does the angle of the mirage tell the wind speed and the cosine of the angle gives a solution relevant to that angle (wind speed)? What am I missing here? Am I over complicating this? Thanks.

Hey Rex how ya doin. First I would like to say I really enjoy your videos. They are very informative. Now to my question. I just finished watching part 32 and you stated that you have to correct for a tail wind. If your bullet is travelling at 3000 fps (2045mph) and you have a tail wind of 10 mph are you not outrunning the wind by 2035 mph?? That is if everything else remains equal( lets just talk about the tail wind and no other factors). So why would you have to correct for it?Thank u!!!

great vid REX!! need to get u a fan page or something

1. an optical phenomenon, by which the image of some object appears displaced above, below, or to one side of its true position as a result of spatial variations of the index of refraction of air. Origin: < French, equivalent to ( se ) mir ( er ) to look at (oneself), be reflected (< Latin mīrārī to wonder at) + -age -age

Which part explains how much to adjust for certain tailwinds or headwinds?

Thanks Bill.

Hey Rex, Any chance you're gonna come up to billings montana in the near future?

Yes, this is amazing

How do you know where the max ordinate is? i.e., how far downrange is it?

Hey Rex, recently ran into your vid series and relearning some things from when I was in S-School 18 years ago and now. I like the more accurate method of using Trig for angles, so I wanted to clarify something from this video. Using the windage value from the table at 1000m (13.7 MOA) in your equation, you end up with a smaller MOA value (9.68 MOA) you're saying is more accurate. In the visual example are you saying that using the FM's full/half value system would have over corrected for the wind? 9.68MOA doesn't seem like enough correction for a 1000m shot, no?

mmh 17:56 Tailwind should be corrected 0.45 MOA down not up

in freezing weather (32 or less) would open free float barrels, as apposed to covered barrels like the Mosin or Lee Enfield, cool faster and lose velocity via slowed burn rate? also I love your videos, fascinating and informative, great job!

could you back off paralex to correct distance and get the correct mirage reading at the top of arc above ground

Oh quick question. How do I figure out what angle my max ordnance is at to focus in on the mirage about 60% down range of target? Say if your shooting 1 mile.

No problem. You are certaily outrunning the wind, but there is still 10mph worth of wind resistance less as you go along. Less resistance will result in a higher retained velocty and thus a raised POI.

Does anyone have a link to a printable table / cheat sheet of the angle cosine method? Thank you

Ahh, Misty Mountain!

thanks

Rex wondering... what is your backgrund.

Rex lets see ballistix gell at long range how much power is at the other end

I have been thinking of buying a aics stock the 1.5 version but the thing is its expensive, or i was thinking macmillan a5 but with surgeon bottom metal thats more than the aics. I was looking at the bell and carlson stocks but all i hear is half good and half bad, and i dont want to be the one buying a stock for no reason. Or a hs precision but still buying a bottom metal it pretty close to the aics and the aics has a adjustable cheek and butt pad, i also like the thumb hole on it so pleas help

Hi Rex ! I was wondering because some people say if you purchased an $ 800 bolt rifle, you could put a 1000 dollar scope or equal to the amount of the price of the rifle or I'm better off with SWFA Super sniper scope based on my budget. Do you think it would be worth the stretch on that hi end scope or SWFA? Please help Im new to this

I have a Ti-83 Plus can someone help me out and tell me why when I hit the cosign button and then 45) exactly how Rex did I got .5253219888? Instead of the .7071067812 as he did?

hey rex nice video, but how do i find the exact deggree that the wind is going with potractor method?

Awesome! Thanks bro!

Good one!

+Jacob S. The reason is that your calculator is set to radians and not degrees .

This is very good and detailed did you use to be a sniper

Ehhhhh, you'll be fine. I'll simplify everything at the end and you'll see how attainable it really is - don't get lost in the forest of details, just keep all this stuff in the back of your mind for later.

great vids

Watching both of these and you not noticed one part of you mentioning the math, what's the math to it?

ok so please tell me if im wrong or what.... so if i have a 2 o'clock wind (22.5 degrees off 3 o'clock) then i use 92% of my full value. does that mean i use the remaining 8% for how much of a head wind i have?

How did you create your cards?

Did you reference the "Misty Mountains" in the Hobbit?

I love your videos but Im starting to think I may never hit anything given all there is to factor.

Wish this was in mils, :(

scope wiggle haha

Can you just come tutor me?

The corrections for deflection that you made in a 3mph wind at 1,000 meters is a gigantic stupidity!!!

just remember SOH.CAH.TOA

thanks