Rifle Scopes MOA Wind Math

[LawnMM]

@LawnMM

The guys I know that started using wind and solvers and spread the word in matches. They used a 29ish InHg to find base wind so it was easy to travel.

As you can see at 6000 feet above sea level or 24inhg, if one tried to use the BC method without understanding the base it would be wrong.

So ya, my 6mph gun becomes a 7 about 26ish and at 24ish an 8 but the guys I learned this from still call their guns by the base wind at 29ish aka 6mph gun.

I think this is a bit like using adjusted barro it helps us all communicate at a base level. I am not suggesting we switch from station, for our solutions, just that if we are going to communicate in a common fashion, mil wind should be distilled to the base formula.

I hope this makes sence, but you have a 6mph system. Where you shoot you need to modify it to a greater value.

If I change to sea level of 29.92 it becomes 6mph like you said. I guess what I fail to understand is how that makes it easy to travel?

If I shoot in Florida it's a 6mph setup, if I shoot in Colorado or Wyoming it's an 8mph setup. If the goal is simplicity and quick wind calls in the absence of time and technology why does it matter?

I've always thought in terms of communication and verbally giving calls to others as in a team setting a 10mph full value wind makes the most sense because it's a language we all speak.

If you try to communicate a call based on this kind of wind call math it would only work if we have the same base number. Because it's a mil or moa number rather than a percentage of a common baseline. Or is that the point? You want to squad with all the 6mph/7mph/8mph or whatever guys?

 

[Diver160651]

If I change to sea level of 29.92 it becomes 6mph like you said. I guess what I fail to understand is how that makes it easy to travel?

If I shoot in Florida it's a 6mph setup, if I shoot in Colorado or Wyoming it's an 8mph setup. If the goal is simplicity and quick wind calls in the absence of time and technology why does it matter?

I've always thought in terms of communication and verbally giving calls to others as in a team setting a 10mph full value wind makes the most sense because it's a language we all speak.

If you try to communicate a call based on this kind of wind call math it would only work if we have the same base number. Because it's a mil or moa number rather than a percentage of a common baseline. Or is that the point? You want to squad with all the 6mph/7mph/8mph or whatever guys?

Sure when that’s where we are shooting together we’d certainly share the info as you suggest.

And we’re kinda saying the same thing, except for the discusion here, using the BC at typical caliber speeds, etc and coming up with a base wind, we are not using Everest nor Death Valley when communication the idea.

It’d be more like your BC of 5.45 @2800 should be 5ish mph gun at sea level; but you’re 200 fps faster so add 1 to the 5 and you have a 6mph gun. So for the sake of the communication of your system, it be the effective BC/Speed.

Now travel to 26inHg and add 1 so it is a 7, 24inHg and it is an 8moh value.

This all done without a solver, as fast as Siri could print this out.

Sure and of course, you should verify with a solver. But the idea is to be able to ball park anywhere using the BC and the medium caliber speeds (around 2800).. then add for speed and reduced mercury.
.

 

[LawnMM]

Good luck with it!

 

[Diver160651]

Perhaps for the purpose of this discussion everyone should stick to standard atmosphere. 59* @ 29.95

Yes, that’s the point sorry if I seemed to detailed or lengthy.

BTW don’t need a Kestrel, any true station device like a Casio, Garmin even a cheap pressure gauge is going to provide good data. Sometimes, especially in regards to humity and baro change in the same location, I think we get overly granular and lost in our devices.

 

[xdeano]

I'll hand it to skookem and subwrx300, there method of finding you mph and using that mph to find your wind by halfing your distance works out pretty spot on for my guns.

I'm using a 6slr for prs and hunting. I feel this quick and dirty method will help me in the field where I don't use a kestrel at all. Don't even bother to bring it with.

Thanks guys!
Xdeano

 

[Deleted member 113831]

I thought I would kind of sum things up a bit. There are a few methods that have been presented, and they all use slightly different ways to get you to your base wind, but summarized as follows:

1) Base wind = 0.3 (1/3) moa per 100 yards = 3 moa @ 1000
2) Base wind = 0.5 (1/2) moa per 100 yards = 5 moa @ 1000
3) Base wind = 1 moa @ 500 and .25 moa adjustments up and down per 100 yards...or, can be figured by 2 x first number of yardline /10, so just move decimal to left 1 place.

There are a few different ways to get to you to your base wind, but for the average shooter here with a ballistics program, it isn't any harder than just plugging in the wind and finding the one that gets you there. For the instructors and AI's who might have to call for multiple people with random guns. The methods for finding base wind to be considered:

Method for #1 above = First number of G1 BC - 1mph seems to work
Method for #2 above = First number of G1 BC + 50%....or first number of entire G7 BC x 3
Method for #2 above (alternate) = G1 + G7 / 100 at 2,500 ft ASL
Method for #3 above = First number of G7 BC + 1mph


@Lowlight, @C_R_Slacker , @300ATT , @Subwrx300

 

[Subwrx300]

I thought I would kind of sum things up a bit. There are a few methods that have been presented, and they all use slightly different ways to get you to your base wind, but summarized as follows:

1) Base wind = 0.3 (1/3) moa per 100 yards = 3 moa @ 1000
2) Base wind = 0.5 (1/2) moa per 100 yards = 5 moa @ 1000
3) Base wind = 1 moa @ 500 and .25 moa adjustments up and down per 100 yards...or, can be figured by 2 x first number of yardline /10, so just move decimal to left 1 place.

There are a few different ways to get to you to your base wind, but for the average shooter here with a ballistics program, it isn't any harder than just plugging in the wind and finding the one that gets you there. For the instructors and AI's who might have to call for multiple people with random guns. The methods for finding base wind to be considered:

Method #1 = First number of G1 BC - 1mph seems to work
Method #2 = First number of G1 BC + 50%....or first number of entire G7 BC x 3
Method #3 = First number of G7 BC + 1mph

@Lowlight, @C_R_Slacker , @300ATT , @Subwrx300

Skook, you might update/add Method 2.5 = Add G1 + G7 entire values. Works at 2500 for most rifles.

G7's tend to be ~50% of the g1 BC and the sum of these two will give a very good base wind value between 5 and 9mph for a given caliber.
Altitude correction for that method is -.5mph per 1000ft below 2500ft reference and +.5 per 1000ft above 2500 reference.

 

[Deleted member 113831]

Skook, you might update/add Method 2.5 = Add G1 + G7 entire values. Works at 2500 for most rifles.

G7's tend to be ~50% of the g1 BC and the sum of these two will give a very good base wind value between 5 and 9mph for a given caliber.
Altitude correction for that method is -.5mph per 1000ft below 2500ft reference and +.5 per 1000ft above 2500 reference.

I'm sorry, I did forget that one. Thank you for posting it up. I'll edit the post above.

 

[CJWhiskus]

Well, here goes. I've been reading through the posts on this thread and confess to being confused by some of it. So, I decided to analyze things in my own way. As I work through research, it works for me to write an explanation to myself. If I can't explain it clearly, then I have missed something along the way and continue to dig. The following is what I wrote. Some of the stuff was mentioned by others in posts and I thank them for that; some is probably in other posts, but I couldn't follow it well enough.

Anyway, this is my understanding of a way to figure windage corrections in the field without a solver or even cards. It looks to be quite accurate.

Warning. It's a bit long and has some simple math.

Anyway, if you read this, thanks for your time and let me know if I'm off base anywhere. I would love to have a method that is simple and works well without batteries.

MOA and Mil Windage Estimation Using Lag Time​

Using the first digit of the G1 BC as the Base Wind is convenient, but it's ballpark and won't necessarily give the least level of error. You also can't use the same Base Wind for both Mil and MOA. It also doesn't account for changes in muzzle velocity or Density Altitude. Here is a way to calculate the Base Wind that I gleaned from an Applied Ballistics book. With it you can calculate the exact Base Wind needed for an MOA setup or a Mil setup.

Where needed, Strelok Pro was used for determining 'actual' windage values, mainly because it supports Density Altitude and fractional wind speeds.

Wind Drift depends on lag time and wind. It can be calculated with a rather simple formula based on these two values. Lag time is the difference between the time of flight in a vacuum (ToFv) and the time of flight in the atmosphere (ToF). How do you get time of flight in the atmosphere? From your ballistic calculator. How do you get the time of flight in a vacuum? Calculate it.

Since we are probably working with a range of 1000 yards, we have 3000 ft divided by muzzle velocity. For example, 3000 ft / 2650 ft/second = 1.132 seconds.

The formula for lag time is: Lag Time = ToF minus ToF(vacuum)

So, Lag Time (DA = 9000 ft) = 1.42 – 1.132 = .288 seconds.

Lag Time (DA = 6000 ft) = 1.46 – 1.132 = .328 seconds.

Lag Time (DA = 2000 ft) = 1.51 – 1.132 = .378 seconds.

These numbers are for a Hornady .264 ELDM 140 gn bullet at 2650 fps. G1 BC is .620

Time of flight in the atmosphere depends on bullet drag. So, the ToF at a DA of 2000 feet will be longer than the ToF at a DA of 9000 feet. This will affect your Base Wind. If you shoot at widely varying DA conditions, you may need to have a different Base Wind for higher and lower DAs.

Now, we want a nice progression of MOA or Mil units that match the convenient 100 yard divisions to 1000 yards. So, we use 0.1 Mil or 0.25 MOA. Ten increments adds up to 1.0 Mil or 2.5 MOA at 1000 yards.

Here's where we calculate the wind needed to move your bullet 1.0 Mil or 2.5 MOA at 1000 yards. Again, the wind needed will not be the same for both units. The formula requires drift at 1000 yards to be in units of inches: so 26.2 inches for MOA or 36 inches for Mils.

The formula is: Drift (in inches) = 17.6 * Wind Speed (in MPH) * Lag Time (seconds)

The 17.6 number is just a constant to convert wind feet per second to miles per hour (per AP).

What we actually want here is the Wind Speed which will be our Base Wind. Drift is how many inches at 1000 yards. This would be the 26.2 inches for MOA and 36 inches for Mil. So we are calculating the wind that would push a bullet 26.2 (or 36) inches at 1000 yards.

We need to rearrange our formula to: Wind Speed = Drift / (17.6 * Lag Time)

Using the above values for MOA: Wind Speed = 26.2 (inches) / (17.6 * .288 seconds) = 5.16 MPH

Using the above values for Mil: Wind Speed = 36 / (17.6 * .288 seconds) = 7.10 MPH

These are both for the 9000 ft DA.

What this means is that a 5.16 MPH wind will move your bullet 0.25 MOA for each 100 yards and 7.10 MPH will move your bullet 0.1 Mil for each 100 yards.

Notice that a different Base Wind is needed depending on the scope units we are using. The math/method between Mil and MOA is the same if you use the proper Base Wind for each.

Wind Drift is not linear, but the MOA progression or Mil progression is. So, we are fitting a linear progression of MOA or Mils to the end points of a curve and there will be some error. If the Base Wind is exact, the biggest errors will be in the mid distances. If the Base Wind is not exact (e.g. rounded) the errors will skew a bit to either the high end or low end.

We probably want to use a whole number for the Base Wind if possible, so we could round 5.16 to 5 MPH and 7.10 MPH to 7 MPH. This will introduce some error. It's a compromise made for ease of in-field calculations. You be the judge on what is acceptable.

Notice that the first digit of the G1 BC is not correct for either MOA or Mils here. Using 6 MPH would introduce substantial errors.

Also, this is Wind Drift only and does not incorporate Spin Drift.

How is this used, you might ask? Here's how.

Let's say you're ready to shoot at a target that is 400 yards away. Your DA is 6000 ft and you have a MOA scope, so your Base Wind is 5 MPH. You have figured the wind and it is (conveniently) a 10 MPH full value wind. You do some quick logic/math in your head that says (something like): “If my Base Wind (5 MPH) will push my bullet 0.25 MOA each 100 yards and the wind is 2 times my Base Wind, it will push my bullet (2 x 0.25 MOA) per 100 yards. That's 0.50 MOA. And since my target is at 400 yards, that's 4 times the value for 100 yards (which is 0.5 MOA now). That's 4 x 0.5 MOA = 2.0 MOA. No Spin Drift needed, so adjust the scope and fire away before the wind changes.”

You would do something similar with a Mil scope, but use the Mil Base Wind with it.

How do you get the wind value? That, as they say, is a whole different can of worms. Science and art as Frank says.

So what about altitude differences? Let's do the calculation for DA = 2000 ft.

Using the above values for MOA: Wind Speed = 26.2 (inches) / (17.6 * .378 seconds) = 3.94 MPH

Using the above values for Mil: Wind Speed = 36 / (17.6 * .378 seconds) = 5.41 MPH

These are both for the 2000 ft DA.

Using the Base Wind of 5 MPH and 7 MPH for the 9000 ft DA at only 2000 ft DA would clearly cause major errors. Similarly, using 4 MPH and 5 MPH at the 9000 ft DA would also cause major errors. Actually rounding 5.41 MPH to 5 would also introduce some degree of error.

Why this change? Additional air density at DA = 2000 ft causes higher drag. The bullet slows faster so there is a longer Lag Time.

Notice that it takes less wind speed at lower altitudes to move the bullet the same amount per 100 yards. That hadn't occurred to me before.

How about muzzle velocity changes?

Let's see how this works out using the previously mentioned Hornady 2.64 ELDM 140 gn bullet at 2650 fps bumped to 2750 fps.

So, Lag Time (DA = 9000 ft) = 1.42 – 1.132 = .288 seconds. 2650 fps.

Lag Time (DA = 9000 ft) = 1.37 – 1.09 = .280 seconds. 2750 fps.

For MOA: Wind Speed = 26.2 (inches) / (17.6 * .280 seconds) = 5.31 MPH

For Mil: Wind Speed = 36 / (17.6 * .280 seconds) = 7.30 MPH

So the Base Wind increased by about 0.15 to 0.20 MPH for each of these. Not a lot, but some additional error. The effect would likely be a bit more at DA = 2000 ft.

So, how much error is introduced by approximating windage with this method?

As long as you use the proper Base Wind for the chosen unit:

DA = 2000 ft, MOA Base Wind rounded up by 0.06 MPH to 4 MPH. Max error is 0.15 MOA at 500 yards, or 0.79 inches. If this Base Wind is (improperly) used for Mils, max error is 0.2 Mils at 500 yards, or 3.6 inches.

DA = 2000 ft, Mil Base Wind rounded down by 0.41 MPH to 5 MPH. Max error is 0.1 Mil at 500 yards, or 1.8 inches. If this base wind is (improperly) used for MOA, max error is 0.7 MOA at 1000 yards, or 7.33 inches.

If both MOA and Mil are used with the appropriate Base Wind, MOA has less error at all ranges at DA = 2000 ft.

Note that rounding the Mil Base Wind by .41 MPH still resulted in 0.1 Mil or less error at all ranges.

DA = 9000 ft, MOA Base Wind rounded down by 0.16 to 5 MPH. Max error is 0.20 MOA at 600 yards, or 1.26 inches. If this base wind is (improperly) used for Mils, max error is 0.3 Mils at 800 yards, or 8.64 inches.

DA = 9000ft, Mil Base Wind rounded down by 0.1 to 7 MPH. Max error is 0.1 Mil at 500 yards, or 1.8 inches. If this base wind is (improperly) used for MOA, max error is 0.9 MOA at 1000 yards, or 9.42 inches.

If both MOA and Mil are used with the appropriate Base Wind, MOA has less error at some ranges, but Mil has virtually zero error at 6 of 10 ranges (at least within the limits of the ballistic solver).

DA = 6000 ft, MOA Base Wind is rounded up from 4.53 to 5 MPH. Max error is 0.2 MOA at 1000 yards, or 2.09 inches. If this base wind is (improperly) used for Mil, max error is 0.2 Mil at 500 yard, or 4.32 inches.

DA = 6000 ft, Mil Base Wind is rounded down from 6.24 to 6 MPH. Max error is 0.1 Mil at 500 yards, or 1.8 inches. If this base wind is (improperly) used for MOA, max error is 0.8 MOA at 1000 yards, or 8.38 inches.

If both MOA and Mil are used with the appropriate Base Wind, MOA has less error at all but one range.

Note that rounding the MOA Base Wind by .47 MPH still resulted in less than 0.25 MOA at all ranges.

So, to recap:

The proper Base Wind for the scope unit used is very important and differs between MOA and Mil.

First digit of the G1 BC is not close enough and sometimes grossly wrong.

Anything that changes the Lag Time will affect the Base Wind (MV, DA, changing bullets).

Base Wind values can apparently be rounded appropriately to the nearest whole number without causing undue error...probably not larger than a scope click unit.

Neither scope unit shows any particular advantage over the other as long as the proper Base Wind is used for each. In fact, if you translate angular errors into 'inches of error' at the target (apples to apples), it appears that MOA has a bit of an edge. Not enough to matter, all things considered.

It doesn't seem that much tweaking or fudging should be needed as long as accurate and proper Base Wind values are used for the scope unit and DA. But, that might just be my lack of experience.

Don't forget to add Spin Drift appropriately if distances exceed 500 yards. From my calculations with my ammunition, this would be .25 MOA at 500,600, and 700 yards, and .50 MOA for 800, 900, and 1000 yards, or the equivalent Mil values.

 

[Diver160651]

This is a runaway train.

No idea why you’d use 9000 to prove the BC estimate for mil wind that’s based on a more stand atmosphere. From there you adjust up. Nobody intended for the extremes to be applied to the suggested starting point for finding your guns mil wind.

I also think a lot of points are being missed when using mil wind. My guess is because people have little practical experience using it and are over analyzing it.

The entire idea is for speed and as an estimate with nothing to complex to remember and as little math as possible. Good mil wind data is as simple taking your already proven drop data in your already used solver and simply moving the mph until the numbers line up. Then when in the field trying use that wind read and think in your guns mph to make a quicker educated guess, because even the Kestrel isn’t right for the entire flight anyway.

 

[Deleted member 113831]

Well, here goes. I've been reading through the posts on this thread and confess to being confused by some of it. So, I decided to analyze things in my own way. As I work through research, it works for me to write an explanation to myself. If I can't explain it clearly, then I have missed something along the way and continue to dig. The following is what I wrote. Some of the stuff was mentioned by others in posts and I thank them for that; some is probably in other posts, but I couldn't follow it well enough.

I appreciate the time and effort it took to write that. I don't know how all that makes it easier to do in the field, though. The idea we have been chasing is easily memorable systems for rapid field use. To address the differences in altitude, it's basically that 4,000 ft is equal to a 1 mph change in base wind, as is a 200 fps change in velocity.

 

[Subwrx300]

Wow... didn't see that coming. Pretty sure Skooks summary had most methods listed well and then this...

 

[Diver160651]

^ Ya, again most of us were using dope cards or just prepared stage cards. We seemed to use a 10mph base FV wherever for whatever system we shot. It seemed easily to look at the wind get an “effective” wind speed then look at our dope card and 1/2, 1/4, or add those parts to the 10mph base. The downside to the kestrels is that you can eat up valuable time, especially if you are first up in the squad. (Most rotate).

A lot of theses matches are memory games. As an example, the stage might have 5 targets, 2 rounds each, fired from each one of 5 positions, in a predetermined sequence all at different ranges- all under a very tight time constraint. Oh btw it is explained only as your squad arrives. Point being, at least me, I am very task loaded. For me, having a simple drop strategy like 200 .5, 300 .1, 400 1.5, 500 2.5 (these are not click accurate) helps me catch errors, like when I use the wrong stage card, write down the wrong drop or someone else has their stage card dopey. The same for wind.

Most people wind strategy even with 308s was cheat into the wind at edge of plate, until the wind value was enough that you had to use a wind error budget. But a lot really weren’t thinking more than, hum, is that wind going to move me off even if I hold wind edge. Later, it seemed to be, grab the kestrel.

FWIW, I heard “what mph are you using for FV" like we always have and do, but started also hearing, "well, I’m using 6mph” long before “mil-wind”. A few guys figured out it was smarter to look at the FV movement to create their wind budget and work that, rather than a 10mph base wind. They cut out a couple of mental steps. The guys did this simply by looking at their solvers and seeing the pattern - no fancy math and no real name.

Move forward and some starts calling it “mil wind”. That made a ton of sense to me. Of course you'd still use old school or at least a combination for those long non-timed ELR shots etc.

Worth repeating, because it seems to have been lost: The really the beauty of mil wind, is it is dead simple, uses the scopes lowest unit and that of course, lines up for most of us click accurate to about 800 using the yardages first digit. 900 & 1000 the same plus .1

It was not until Mike from @Mile High Shooting, the mentioned BC method that I realize he was showing another way to talk and arrive at "mil wind" rather than do what some of us were doing, using our solver to find our mph.

@Skookum went a step further and looked at the patterns to create addition rules of thumb for elevation and speed even without a solver handy. However, if I am traveling with a ton of elevation or temp change, I simply run the new expected temp and altitude thru my solver for the new adjusted mil-wind. Skookum has also been super patient trying to explain “how” it works, recapping the best alternative methods people have put forth.

From my eyes, all this all was ment to be simple, reduce the task loading, have strategy better than "edge of plate plus a little more" and just be easy.

Again all this is a short cut for simplicity and speed. If we forget that we have completely missed the boat. Unfortunately, while you can drive hard to get something for MOA, it just is NOT as simple, there is no way around it.

 

[Lowlight]

There are a dozen ways to skin any kind of math cat,

what we are looking to do is give guys a leg up when they don't have the time or experience to develop their own system. Instead of defaulting to 1960s longhand math formulas with a constant meant for something else. We are hoping to get you to understand quick, simple information that will translate to your system.

Once you have that basic data for your system, like what MPH to use which gives you the simplest solution to remember, translating that data across conditions will hopefully make it easier.

Most guys try the "the everything against the wall and see what sticks approach" we know there are several different methods of determining your wind hold. In both Mils and MOA, however, if we can get new shooters a simple page quickly, they will that much more effective. Even the databoks can use this information vs repeating the old longhand math nobody is doing in the field.

For all the information out there, many dismiss it or not use it because it's an information overload and just looking at the formulas will cause them to ignore them.

Again, it's this

0 + 4 = 4
1 + 3 = 4
2 + 2 = 4
5 - 1 = 4

We can reach the # 4 in a host of different ways, which one sticks with you is up to you, but if we give you the easiest way to reach it vs a formula, hopefully, that clicks.

 

[Diver160651]

There are a dozen ways to skin any kind of math cat,

what we are looking to do is give guys a leg up when they don't have the time or experience to develop their own system. Instead of defaulting to 1960s longhand math formulas with a constant meant for something else. We are hoping to get you to understand quick, simple information that will translate to your system.

Once you have that basic data for your system, like what MPH to use which gives you the simplest solution to remember, translating that data across conditions will hopefully make it easier.

Most guys try the "the everything against the wall and see what sticks approach" we know there are several different methods of determining your wind hold. In both Mils and MOA, however, if we can get new shooters a simple page quickly, they will that much more effective. Even the databoks can use this information vs repeating the old longhand math nobody is doing in the field.

For all the information out there, many dismiss it or not use it because it's an information overload and just looking at the formulas will cause them to ignore them.

Again, it's this

0 + 4 = 4
1 + 3 = 4
2 + 2 = 4
5 - 1 = 4

We can reach the # 4 in a host of different ways, which one sticks with you is up to you, but if we give you the easiest way to reach it vs a formula, hopefully, that clicks.

Glad to see you Back!!

 

[Deleted member 113831]

Once you have that basic data for your system, like what MPH to use which gives you the simplest solution to remember, translating that data across conditions will hopefully make it easier.

@CJWhiskus
This ^^^^ is the heart of the matter right here. Knowing the "Base Wind" for your gun, and simply knowing what multiplier to use for the range in a full value wind. How you calculate it is up to you. It doesn't have to be any harder in MOA than MILS, you just use a different multiplier.

Knowing the tweaks for altitude and velocity aren't going to be helpful to everybody. Not everybody spends a lot of time with different rifles and cartridges at long range, or commonly travels between Florida and the Rockies to shoot comps or classes. Those that do, have ballistic solvers that they can reference to tell them what thier adjusted Base Wind is.

However, if you are an instructor who lives or works in a place like Florida or Colorado, and there are students coming in from all over the country to your class, you may want to know how differently thier bullets are gonna fly at your class, without breaking out the ballistic calculator and running numbers for every single one.

If you know the trends, you can simply ask the student while he is on the line, "What is your BC and speed?" this allows you to instantly assign him a Base Wind in MPH....and you are off to the races.

 

[Diver160651]

It doesn't have to be any harder in MOA than MILS, you just use a different multiplier.

While I agree with most of what you are saying and REALLY applaud what you done to help simplify the MOA wind, it is hard for me to buy 100% that they are both as simple as each other.

Take your recap of how to apply our guns mph:

1) Base wind = 0.3 (1/3) moa per 100 yards = 3 moa @ 1000​

2) Base wind = 0.5 (1/2) moa per 100 yards = 5 moa @ 1000​

3) Base wind = 1 moa @ 500 and .25 moa adjustments up and down per 100 yards...or, can be figured by 2 x first number of yardline /10, so just move decimal to left 1 place.​

​

Method for #1 above = First number of G1 BC - 1mph seems to work​

Method for #2 above = First number of G1 BC + 50%....or first number of entire G7 BC x 3​

Method for #2 above (alternate) = G1 + G7 / 100 at 2,500 ft ASL​

Method for #3 above = First number of G7 BC + 1mph​

​

Lets just say I am at 7oo yards what is my MOA wind adjustment if my base at FV? What is adjustment at 700 with mil base FV? The first number with a dot in front. Sure you can do some quick math with MOA and it works, but I don't want to do that much math target to target on a stage as an example or even hunting.

Again, not to take away from the great work done here, but the moment we say they are just as simple, discredits reality.

If I saw a new shooter asking what is easier, what system should I buy and they are not wanting to be a paper discipline person, the simplicity of mil-wind should make their choice a no brainer.

​

 

[Deleted member 113831]

While I agree with most of what you are saying and REALLY applaud what you done to help simplify the MOA wind, it is hard for me to buy 100% that they are both as simple as each other.

Take your recap of how to apply our guns mph:

1) Base wind = 0.3 (1/3) moa per 100 yards = 3 moa @ 1000​

2) Base wind = 0.5 (1/2) moa per 100 yards = 5 moa @ 1000​

3) Base wind = 1 moa @ 500 and .25 moa adjustments up and down per 100 yards...or, can be figured by 2 x first number of yardline /10, so just move decimal to left 1 place.​

​

Method for #1 above = First number of G1 BC - 1mph seems to work​

Method for #2 above = First number of G1 BC + 50%....or first number of entire G7 BC x 3​

Method for #2 above (alternate) = G1 + G7 / 100 at 2,500 ft ASL​

Method for #3 above = First number of G7 BC + 1mph​

​

Lets just say I am at 7oo yards what is my MOA wind adjustment if my base at FV? What is adjustment at 700 with mil base FV? The first number with a dot in front. Sure you can do some quick math with MOA and it works, but I don't want to do that much math target to target on a stage as an example or even hunting.

Again, not to take away from the great work done here, but the moment we say they are just as simple, discredits reality.

If I saw a new shooter asking what is easier, what system should I buy and they are not wanting to be a paper discipline person, the simplicity of mil-wind should make their choice a no brainer.

​

It's as easy as: MILS method, 700 =0.7 MILS (7 x 0.1).....3 MOA method, 700 = 2.1 MOA (7 x 0.3).......5 MOA method, 700 = 3.5 MOA (7 x 0.5)

I guess I don't get how it's harder. You have to do a small amount of math to scale the actual wind and wind direction anyway.

 

[Diver160651]

It's as easy as: MILS method, 700 =0.7 MILS (7 x 0.1).....3 MOA method, 700 = 2.1 MOA (7 x 0.3).......5 MOA method, 700 = 3.5 MOA (7 x 0.5)

I guess I don't get how it's harder.

Because we are currently doing the math at our computers, not with 90 seconds trying to build you new position for 5 moves and looking for the target while your reading the current wind.. It looks easy and similar when you type it out. But were not really think in terms of multiplication in mil wind 700 is 7 automatically .7 in our head

700 is 7 (only the expression makes it look similar). 700 is something you have to do real multiplication to get in MOA. But remember, the head math all gets at least one more step. Basically have no steps in mil wind, use the first number then yes now the wind value. In the case of 3/4 value, I can with little mental resources look at 7 and say .5mil. If I have one more true multiplication in the step the level of focus is just not the same in my head while I am doing other stuff. So I have 7x.3 is 2.1,fair enough, it become 2MOA simple and now 3/4 value of 2MOA = easy on the computer, but I have to track and truly multiple - it is another step.

If someone thinks I am making a mountain out of a mole hill.. Come to a positional match and watch a new shooter just try to find the target after they built their position. New shooter's time out on their first targets a lot, use the wrong dope cards, shoot at the wrong targets, forget to open their bolts on move, forget the adjust for the wind, forget to spin their turrets, being off one rev. I see this all the time and have done all of the above. Task loading is real.. every step you can cut is huge.. It just is not the same when we are away from the computer.

Edited to add: I am not saying the methods that have been discussed are anything less that great.. It is just that mil wind is simpler

 

[Deleted member 113831]

Because we are currently doing the math at our computers, not with 90 seconds trying to build you new position for 5 moves and looking for the target while your reading the current wind.. It looks easy and similar when you type it out. But were not really think in terms of multiplication in mil wind 700 is 7 automatically .7 in our head

700 is 7 (only the expression makes it look similar). 700 is something you have to do real multiplication to get in MOA. But remember, the head math all gets at least one more step. Basically have no steps in mil wind, use the first number then yes now the wind value. In the case of 3/4 value, I can with little mental resources look at 7 and say .5mil. If I have one more true multiplication in the step the level of focus is just not the same in my head while I am doing other stuff. So I have 7x.3 is 2.1,fair enough, it become 2MOA simple and now 3/4 value of 2MOA = easy on the computer, but I have to track and truly multiple - it is another step.

If someone thinks I am making a mountain out of a mole hill.. Come to a positional match and watch a new shooter just try to find the target after they built their position. New shooter's time out on their first targets a lot, use the wrong dope cards, shoot at the wrong targets, forget to open their bolts on move, forget the adjust for the wind, forget to spin their turrets, being off one rev. I see this all the time and have done all of the above. Task loading is real.. every step you can cut is huge.. It just is not the same when we are away from the computer.

OK, I will concede every point you made, but this isn't a "MILS vs MOA" thread. This is a "How to do it better and easier in MOA" thread.

 

[Diver160651]

OK, I will concede every point you made, but this isn't a "MILS vs MOA" thread. This is a "How to do it better and easier in MOA" thread.

Yes, your correct.

I jumped in only to illustrate how important it s to keep it completely simple. Even with the great formulas you guys came up with it still carries a tiny bit of extra baggage. Nobody should try to unpack it more, unless their is a new way to make it even more streamlined and easier.

For someone to kinda undo that work with long drawn out ways even if they seem a 1/4 moa more accurate in some cases, seems they do not understand the history or lost the main point of why one might want to use the same premise that the mil wind guys are, but with MOA.

Sorry if my ramblings aren't clear.

 

[300ATT]

Hunt and peck with your solver to find the FV base windspeed at your location such that the required wind hold (in MOA) = 1/2 (distance in yards)/100.

or
100 = 0.5 MOA
200 = 1.0 MOA
300 = 1.5 MOA
400 = 2.0 MOA
500 = 2.5 MOA
600 = 3.0 MOA
700 = 3.5 MOA

and so on ...

For one of my .308's ("El Gordo"), using this simple MOA method requires a base FV windspeed that is approximately 40%-50% more than the windspeed needed for the Mil method. According to my ballistics solver this is roughly 7.5 mph (here in CO with a DA of 5,500). The Mil method requires I use a base FV windspeed of 5.0 mph which gets me .1 mils per 100 yards out to 900. Using 7.5 mph FV base wind gets me 1/2 the distance in MOA out to 900 yards per above.

This will get you very close within less than 1/4 MOA (which none of us can hold anyway) and it doesn't get any easier to remember and compute - simple.

 

[CJWhiskus]

Diver160651

Thanks for your comment. Bear in mind that this was primarily an exercise for me to learn the about the physics of wind drift within the context of determining Base Wind accurately. Then to determine how accurately that predicted bullet behavior and then how sensitive that accuracy was to altitude and MV variations. It was never intended to be field math of any kind, except in so far as an accurate Base Wind calculated beforehand would be useful. The result is a direct calculation that avoids estimates based on whatever the BC method was originally based on. I don't know if that is useful to anyone but me or not. I posted it so others could have it if they wanted.

The DA = 9000 ft wasn't included to prove or disprove anything. It was included as an extreme upper example of atmospheric conditions that could be compared to a mid and low example to investigate how sensitive a true base wind was to this parameter. BTW, a 9000 ft DA is my typical summer conditions in the high deserts of Utah. Likewise 6000 ft DA is my typical winter conditions. They are practical conditions to me. The result is useful to my own shooting.

I also wasn't trying to investigate anything about Mil wind except the calculation of an accurate Base Wind and determination of it's predictive accuracy. From the posts on this forum, there seems to be several empirical ways to arrive at mil wind mechanisms that satisfy their users. That's fine. I have no skin in that game. I wanted to eliminate as many errors as possible so I could examine sensitivity to atmospheric factors. So, I chose a mathematical method.

Skookum

Thanks. It doesn't make it any easier to do in the field. It's just a method to very accurately determine a Base Wind value and get a little insight into the air density sensitivity. If this method calculates a better value, calculate a value and take it to the field and use it. If your method works for you, by all means continue to use it.

I agree with you on the 1 MPH change in Base Wind for 4000 ft altitude change. The Base Wind value doesn't seem to change much from 5000 to 9000 DA, but from 5000 down to 1 or 2000 DA it does change by 1 MPH. Most might not care. If Frank has students come from Texas to Colorado, then they will experience a change.

Frank

Your needs for classes seems to be somewhat different from other posters. What I hear you saying from your videos and here is that the BC method works well enough for you to teach/manage students with Mil scopes, but you need a correspondingly simple method to use for people with MOA scopes. I'm sure adding some math in there involving Lag Time wouldn't be helpful. Correct me if I'm wrong here. I'm just trying to understand better what the holy grail is. It kind of sounds to me like there needs to be a way to scale the Mil Base Wind that would adjust it for a correct MOA Base Wind for .25 MOA units. Would the rest fall in place then?

Diver160651

I think Skookum's statement about MOA vs Mils is exactly right within certain parameters. I calculated Base Wind for both MOA and Mils under exactly the same conditions, using .1 Mil and .25 MOA. The Base Wind values were different between the two because they had to be. But if you use the Mil Base Wind for the Mil solution and use the MOA Base Wind for the MOA solution, the result is almost identical if you are using .25 MOA increments. The problem seems to be in how to determine the MOA Base Wind for .25 MOA increments without math. Apparently the Mil BC determination works well enough for most, but doesn't do as well for MOA.

Interesting discussion.

 

[CJWhiskus]

Hey. Thanks for the likes!
Following up on some way to scale the Mil Base Wind values to MOA values, I discovered it is trivial IF you have a Mil Base Wind accurate to a couple of decimal places. You just multiply Mil wind by 0.72. But, as soon as you have a rounded Mil value, it doesn't work very well. I looked for other patterns, but didn't find any. So, I generated some tables with two calibers and 3 different brand bullets across each caliber that have different G1 values. I attached them as a .pdf. I haven't carefully proofed them for errors, but I think they are substantially correct. Don't take them as gospel...just some examples.

The first thing I noticed is that different bullets defy using the first BC digit for Base Wind. I don't know the history of that, but I could surmise it came from the .308 168gn MK at modest DAs...a lot of 4s in that column. The newer high BC bullets behave a differently, even between brands with similar BCs.

At this point, I'm thinking that the only way to get good values for MOA without doing the Lag Time bit is using tables like this. The gotcha is that bullets come and go and tables will have to be updated periodically.

@Lowlight

I'm thinking that tables like these might be your only option. New bullets and new calibers have made the first digit BC pretty shaky. You could hand them out to students and coach them on how to find the Base Wind for their bullet and scope unit...either one actually so the Mil guys get a good value too. They can take them home and use them for their local conditions as well. Could make data book pages with them. Once each student has their Base Wind, the use of it should be independent of the scope unit.

I just chose a few bullets and calibers that might be common in your classes to see if there were commonalities or patterns. I don't see any. I don't know what people bring to class, but, of course, the tables could be expanded to cover the ground. I won't pursue it any further if it's not useful to you.

Jim

 

[pitdog85]

Everything here is understandably US based in yards, will any of this work for those of us using MOA scope but ranges in metres?? I must admit most of this thread is way beyond me I don't honestly think I can crunch any of these calculations in my head on the firing line but I guess anything can be improved with practice.

 

[Deleted member 113831]

Everything here is understandably US based in yards, will any of this work for those of us using MOA scope but ranges in metres?? I must admit most of this thread is way beyond me I don't honestly think I can crunch any of these calculations in my head on the firing line but I guess anything can be improved with practice.

Yes, remember that for either unit of angular measurement you are simply choosing a wind speed that gives you a particular angle of drift at 1000 units, be it yards or meters. I like to use a 5 MOA drift at 1000 yards for MOA. That gives me 1/2 (0.5) MOA per hundred units drift. But it would work for 1000 meters just as well.

Given: A 6.5 caliber, 140 grain Hornady (.646 G1) ELD-M at 2800 fps at sea level. ( I seem to remember you being at sea level)

A 7 mph wind will push you 4.9 MOA at 1000 meters. That will keep you to within 1/2 MOA of actual drift all the way to 1000 meters.

For something like a 308 at 2650 fps ( .505 G1) a 5 mph wind will push you 5.3 MOA at 1000 meters. Again, keeping you with 1/2 MOA all the way to 1000 meters.

The difference between the MIL and MOA basic winds is almost completely offset by the difference in linear distance between yards and meters. So a bullet that is a "5" when using yards and MILS, is still very close to a "5" when using MOA with meters.

Clear as mud?

 

[pitdog85]

Yes, remember that for either unit of angular measurement you are simply choosing a wind speed that gives you a particular angle of drift at 1000 units, be it yards or meters. I like to use a 5 MOA drift at 1000 yards for MOA. That gives me 1/2 (0.5) MOA per hundred units drift. But it would work for 1000 meters just as well.

Given: A 6.5 caliber, 140 grain Hornady (.646 G1) ELD-M at 2800 fps at sea level. ( I seem to remember you being at sea level)

A 7 mph wind will push you 4.9 MOA at 1000 meters. That will keep you to within 1/2 MOA of actual drift all the way to 1000 meters.

For something like a 308 at 2650 fps ( .505 G1) a 5 mph wind will push you 5.3 MOA at 1000 meters. Again, keeping you with 1/2 MOA all the way to 1000 meters.

The difference between the MIL and MOA basic winds is almost completely offset by the difference in linear distance between yards and meters. So a bullet that is a "5" when using yards and MILS, is still very close to a "5" when using MOA with meters.

Clear as mud?

Thanks again mate I will run my Bullet through jbm and see if I can find what your saying I'm running a 139 scenar at 2700 at sea level

 

[Deleted member 113831]

Thanks again mate I will run my Bullet through jbm and see if I can find what your saying I'm running a 139 scenar at 2700 at sea level

I ran your numbers. 139 Scenar ( .578 G1) @ 2700 fps @ sea level.

JBM says a 6 mph full value wind will give you 5.1 MOA at 1,000 meters at sea level. So, 0.5 MOA per hundred meters.

This should put you to within 1/2 Minute of actual drift at all ranges to 1,000 meters.

 

[pitdog85]

I ran your numbers. 139 Scenar ( .578 G1) @ 2700 fps @ sea level.

JBM says a 6 mph full value wind will give you 5.1 MOA at 1,000 meters at sea level. So, 0.5 MOA per hundred meters.

This should put you to within 1/2 Minute of actual drift at all ranges to 1,000 meters.

Yup thanks again that's exactly what I found 6mph

 

[Rillhurst]

Tag

 

[pitdog85]

Ok so I have being playing with JBM and I need math help. I have the 6mph worked out it moves the bullet 5moa at 1000, and 0.5 moa every hundred perfect. I cannot work out how to do the calculation if the wind is for example 9mph or 14mph or 4mph?? Is it possible to work these out in your head or is this moa wind more of a rough estimate ie I know 6mph moves my bullet this much at each distance for other wind speeds kinda just guess based off this 6mph ie add a bit more for 9 or a bit less for 4??

 

[_Windrider_]

Ok so I have being playing with JBM and I need math help. I have the 6mph worked out it moves the bullet 5moa at 1000, and 0.5 moa every hundred perfect. I cannot work out how to do the calculation if the wind is for example 9mph or 14mph or 4mph?? Is it possible to work these out in your head or is this moa wind more of a rough estimate ie I know 6mph moves my bullet this much at each distance for other wind speeds kinda just guess based off this 6mph ie add a bit more for 9 or a bit less for 4??

At 9mph you would add .25, call it .3 Mils.

 

[Deleted member 113831]

At 9mph you would add an additional .25, call it .3 MOA.

Fixed it for you.

 

[_Windrider_]

Fixed it for you.

10-4 good buddy

 

[spife7980]

At 9mph you would add .25, call it .3 Mils.

Would you say that is because 9 mph is a 50% increase in speed over a 6 mph wind?
So 9/6=1.5x correction factor
.5 per hundred x 1.5 correction for more wind=.75 per hundred and rounded up is a hold of .8?
And .8- the.5 base mph is the .3 more you described for the 9mph wind?
(Trying to lay the math out for him, not question you)

 

[Nik S]

Just a note of thanks for making the complex simple once again.

I get that this is an attempt to simplify MOA math, but even the Mil B.C. Base wind method was an eye opener at my level of understanding.

Nik

 

[Snuby642]

I am fully prepared to be used as a kickball so here it goes.
Have read this thread and the mil thread.
Lots of math being preformed still in both.

I have finaly figured a way (with all your help )for me to get what appears to be my mph gun value.
In fact could be in kt and or meters, moa or mil.

Was doing the math and playing with a balistic solver.

All I have to do is set my solver environmentals for where I go to shoot.

Set my wind full value 90/270 and add wind till I get 1 click worth at 100.
Then add distance to see if that wind value increases with each 100 yards or meters to 1000.

So according to this I have a 3mph 6.5 Grendel.
This held constant to 800yd and needed 1 click more begining at 900.

20in 6.5 grendel hornady custom (for now) 123gr sst @ 2580fps G1 .510

Any decent solver, hold press button follow through this should be your gun mph value.

I dont think it matters what scope or measurement you wish to use.

Or I haven't learned a damn thing?

Ok. Start kicking.

 

[Billiam1211]

Just as a data point =>

At my last PRS match I was able to clean the KYL rack @ 400 yards. I'm running a 6.5 Creedmoor w/ 140gr ELDs going 2,793 fps and JBM called for 2 MOA at 400 yards for a 10mph wind.

I held 2 MOA off center of the largest plate and noticed that my impact still wasn't center. On the last 3 targets I bumped my hold to 3 MOA and it ended up working out. A guy with a kestrel said the wind was hovering around 15 mph.

 

[Geno C.]

I am fully prepared to be used as a kickball so here it goes.
Have read this thread and the mil thread.
Lots of math being preformed still in both.

I have finaly figured a way (with all your help )for me to get what appears to be my mph gun value.
In fact could be in kt and or meters, moa or mil.

Was doing the math and playing with a balistic solver.

All I have to do is set my solver environmentals for where I go to shoot.

Set my wind full value 90/270 and add wind till I get 1 click worth at 100.
Then add distance to see if that wind value increases with each 100 yards or meters to 1000.

So according to this I have a 3mph 6.5 Grendel.
This held constant to 800yd and needed 1 click more begining at 900.

20in 6.5 grendel hornady custom (for now) 123gr sst @ 2580fps G1 .510

Any decent solver, hold press button follow through this should be your gun mph value.

I dont think it matters what scope or measurement you wish to use.

Or I haven't learned a damn thing?

Ok. Start kicking.

Works out damn close for my 6brx at 2926 with a 105hybrid. 5mph is a click per 100
out to about 900 where you add one.

When my da drops to about 100 I have to add one at 700

 

[Deleted member 113831]

I am fully prepared to be used as a kickball so here it goes.
Have read this thread and the mil thread.
Lots of math being preformed still in both.

I have finaly figured a way (with all your help )for me to get what appears to be my mph gun value.
In fact could be in kt and or meters, moa or mil.

Was doing the math and playing with a balistic solver.

All I have to do is set my solver environmentals for where I go to shoot.

Set my wind full value 90/270 and add wind till I get 1 click worth at 100.
Then add distance to see if that wind value increases with each 100 yards or meters to 1000.

So according to this I have a 3mph 6.5 Grendel.
This held constant to 800yd and needed 1 click more begining at 900.

20in 6.5 grendel hornady custom (for now) 123gr sst @ 2580fps G1 .510

Any decent solver, hold press button follow through this should be your gun mph value.

I dont think it matters what scope or measurement you wish to use.

Or I haven't learned a damn thing?

Ok. Start kicking.

You find your mph at distance, not at 100 yards.

Your gun would be a 4mph gun at 2k ft elevation the way I figure it. It would be 3.5mph at sea level. Your ballistics are pretty identical to a 308 175SMK at the same speed.

Small differences at the closer ranges don't matter.

 

[Deleted member 113831]

Just as a data point =>

At my last PRS match I was able to clean the KYL rack @ 400 yards. I'm running a 6.5 Creedmoor w/ 140gr ELDs going 2,793 fps and JBM called for 2 MOA at 400 yards for a 10mph wind.

I held 2 MOA off center of the largest plate and noticed that my impact still wasn't center. On the last 3 targets I bumped my hold to 3 MOA and it ended up working out. A guy with a kestrel said the wind was hovering around 15 mph.

That math works out pretty spot on.

 

[Snuby642]

I would like a couple of people that have known gun wind for thier rifles to test this and see if it lines up with thier dope.

Also any shooters running meters and kph please.

I am fully prepared to be used as a kickball so here it goes.
Have read this thread and the mil thread.
Lots of math being preformed still in both.

I have finaly figured a way (with all your help )for me to get what appears to be my mph gun value.
In fact could be in kt and or meters, moa or mil.

Was doing the math and playing with a balistic solver.

All I have to do is set my solver environmentals for where I go to shoot.

Set my wind full value 90/270 and add wind till I get 1 click worth at 100.
Then add distance to see if that wind value increases with each 100 yards or meters to 1000.

So according to this I have a 3mph 6.5 Grendel.
This held constant to 800yd and needed 1 click more begining at 900.

20in 6.5 grendel hornady custom (for now) 123gr sst @ 2580fps G1 .510

Any decent solver, hold press button follow through this should be your gun mph value.

I dont think it matters what scope or measurement you wish to use.

Or I haven't learned a damn thing?

Ok. Start kicking.

Edit: @lowlight
Now I'm asking for a kicking. Lol