Advanced Marksmanship Rule of 9s (wind holdover)

[_S2_]

If this has been posted before I apologize, I did some searching and didn't come up with anything.

A few years ago while on a quest to get more training in Iraq on my BRAND NEW M24 (I was a SDM, did the 2 week LRM course...long story), I visited our local friendly ODA compound for some knowledge.

I was shown the light with the Rule of 9's and I was wondering if anybody else has had great success with this or any other "versions" of it that worked out better.

Basically...
Take the wind speed in mph and multiply it by the base number of the range in meters.

Example - <span style="font-weight: bold">3</span> mph @ <span style="font-weight: bold">5</span>00 M = 15

Now each 1/4'd mil is 9, so 1 mil is 36 (9,18,27,36,45,54,etc). Knowing this we take the 15 and figure that it is close to 18 ( 1/2 Mil ). So we say our holdover is going to be light 1/2 hold.

I personally had some good success with it. Anybody have an idea if a similar formula works for the M107 using Mk211?

 

[Scottmilk9]

Re: Rule of 9s (wind holdover)

S2,
The solution is intriguing. I'll look at it more. Thanks


Just an fyi, you should fill in your profile before someone comes down on ya.

thanks for the post.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

So if I'm reading this right, let's try another:

10mph at 500=50, 50is close to 1.5 mils (9x6 quarters=54) so a light mil and a half hold? Am I doing this right?

Problem is that 10mph at 500m for my rifle running M118 is 1 mil, so I'd be holding just under a half mil to much.

Or we can try another:

5mph at 800 would be 40, giving us between a mil and a mil and a quarter. Actual M118 dope for my 308 at 800m for 5mph is just under one mil (.8-.9), still within a half mil.

Not bad, again:

10mph at 900m=90, 90/9=10, so 10 quarters=2.5mil
Actual dope for 900m 10mph is 2.3, so we're within a half mil again.

I think in the absence of a dope card this system would get you "close enough for gov't work".

Maybe someone else can run the math for the requested 556 load, my guess is that within 600 yards it would work.....

 

[Lindy]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">MAybe someone else can run the math for the requested 556 load, my guess is that within 600 yards it would work....</div></div>

If you meant where he said, <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...similar formula works for the M107 using Mk211.</div></div>

The M107 is a .50, and Mk211 is Armored Piercing Incendiary for it.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

DOH!!

Reading while tired again, blurred over and was thinking MK12 M262.....

 

[Pat M]

Re: Rule of 9s (wind holdover)

mark, to reread when i'm not too tired to forget

good post

 

[Mo_Zam_Beek]

Re: Rule of 9s (wind holdover)

This works.

Here is an alternate formula:

Dist in yrds (/10) x Wind Velocity / Constant = MOA of hold

Constants:

0-500 = 15
600 = 14
700 = 13
800 = 12
900 = 11
1k = 10

Therefore looking at the following examples:

350 yrds / 3 MPH = 0.2 MIL
600 yrds / 8 MPH = 0.99 MIL
725 yrds / 15 MPH = 2.44 MIL

Using the 'Rule of 9's' (and converting yrds to meters):

320 meters / 3 MPH = 0.25 MIL
549 meters / 8 MPH = 1.25 MIL
663 meters / 15 MPH = 2.75 MIL


Good luck

 

[Mo_Zam_Beek]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _S2_</div><div class="ubbcode-body">

Example - <span style="font-weight: bold">3</span> mph @ <span style="font-weight: bold">5</span>00 M = 15

Now each 1/4'd mil is 9, so 1 mil is 36 (9,18,27,36,45,54,etc). Knowing this we take the 15 and figure that it is close to 18 ( 3/4 Mil ). So we say our holdover is going to be light 3/4 hold.
</div></div>

You mean 1/2 MIL - correct?



Good luck

 

[_S2_]

Re: Rule of 9s (wind holdover)

Yes sorry, light 1/2 hold, and I edited the post to reflect that.

This is definitely a close enough sort of formula, hence the reason I was posting to see if anybody had anything that differed but was along the same principle and worked better. I don't think this formula works real well past 600 M, the drop off the of the round is too much + the wind.

I am very familiar with Maj. Plaster's book, it basically kept me alive and shooting bad guys throughout my deployment. It's even signed by him.

 

[Lindy]

Re: Rule of 9s (wind holdover)

Here's a simple one I built using this formula:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
(range in yards/100) * wind (mph)
wind hold(mils) = ----------------------------------
constant
</pre></div></div>

The constants I use are:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
Range(yards) Constant
<= 500 45
600 43
700 41
800 39
900 38
1000 37
</pre></div></div>

However, that's a rough approximation for my .308 load. If you want one more accurate, use a ballistic program set up for your load and a 1 mph full-value crosswind, and work the formula backwards:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
(range in yards/100) * wind (mph)
constant = ----------------------------------
wind hold(mils)
</pre></div></div>

 

[DaveV]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _S2_</div><div class="ubbcode-body">I am very familiar with Maj. Plaster's book, it basically kept me alive and shooting bad guys throughout my deployment. It's even signed by him. </div></div>

You don't read that very often around these parts...lot's of Plaster hate here

Thanks for your service and the cool rule of thumb (9's in this case)

 

[CoryT]

Re: Rule of 9s (wind holdover)

Someone please explain what a 'light 1/2 mil' is? It's either .4, .5, or .6, unless you can hold .05 or the like. Since I don't know anyone who can do that, this light / heavy nonsense is just that. Just use tenths, that's probably as good as anyone can hold and surely as good as anyone can read wind.

 

[_S2_]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body">Someone please explain what a 'light 1/2 mil' is? It's either .4, .5, or .6, unless you can hold .05 or the like. Since I don't know anyone who can do that, this light / heavy nonsense is just that. Just use tenths, that's probably as good as anyone can hold and surely as good as anyone can read wind.</div></div>

A light 1/2 hold is basically a .4 hold. The light / heavy "nonsense" was just a TTP that myself and the other SDM/spotter used. Tenths of a mil wasn't used since it isn't a precise hold, its just something rough and dirty that generally gets the round on target. Besides, it isn't like our scopes have tenths hash marks, you have to eyeball tenths as much as you do .25, .5, and .75.

Something about the mentality of it clicked with us, not being too concerned about the exact mil hold, but just saying "eh just somewhere shy of a 1/2 mil and shoot before he goes around that corner sort of thing.". It made us comfortable with our ability to shoot with wind by simplifying it I guess.

 

[TOP PREDATOR]

Re: Rule of 9s (wind holdover)

at those ranges, why use a rule of thumb?

you are most likely going to have enough time to take a wind reading, observe what it's doing down range, look at your data book, make a calculation, then make an actual optic adjustment to take a precise shot and a higher percentage hit rather than a guesstimate.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TOP PREDATOR</div><div class="ubbcode-body">most likely </div></div>

Best reason to have a backup plan in your head.

I'm gonna pocket this little formula to use if I need to later for sure.

 

[sniperaviator]

Re: Rule of 9s (wind holdover)

For 308 at sealevel 2700fps
per 1mph wind
1000yds 1moa
900 .9moa
800 .8moa
etc

So for 10mph wind its
1000 10 moa
900 9 moa
800 8 moa

 

[zunrj5]

Re: Rule of 9s (wind holdover)

The "rule of 9s" works pretty well for what it is. It's not a bad tool if you need to do a quick calculation in your head (or on your fingers), as long as you understand its limitations. Like any other quick formula, once you've played with it for a while you'll get a feel for when to cut or when to add.

-John

 

[Mr Flannel]

Re: Rule of 9s (wind holdover)

How would this work if you calculate wind speed in KPH?

We're all metric down here...

 

[Mo_Zam_Beek]

Re: Rule of 9s (wind holdover)

Priest - they are just constants. I don't think in terms of the metric system (admittedly it is a substantially more logical system) so I don't have the specific answer for you. None the less, either play with a ballistic calculator and back your way into the constants or hope Lindy sees this b/c I would not be surprised if he just carries that data around in his head.


Good luck

 

[SierraOne1]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">Here's a simple one I built using this formula:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
(range in yards/100) * wind (mph)
wind hold(mils) = ----------------------------------
constant
</pre></div></div>

The constants I use are:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
Range(yards) Constant
<= 500 45
600 43
700 41
800 39
900 38
1000 37
</pre></div></div>

However, that's a rough approximation for my .308 load. If you want one more accurate, use a ballistic program set up for your load and a 1 mph full-value crosswind, and work the formula backwards:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
(range in yards/100) * wind (mph)
constant = ----------------------------------
wind hold(mils)
</pre></div></div>
</div></div>

OK, Lindy. I can't seem to make these numbers work.

I set my program to full-value, 1mph and the windage is reading in MIL's.

@ 500yds, it shows .29 MILS of windage.

When I run the formula to find the constant, I'm getting nothing CLOSE to your constants (I'm in the teens).

Here's how I construed what you wrote:

1. 500yd/100=5
2. 5 X 1mph =5
3. 5 / .29 (what my program lists as the required MIL-hold) = 17 (constant)

But when I use that I'm getting a FUBAR'd answer. For example, with a 12MPH wind at 500yds using that 17 constant, I'm getting 3.5 MILs of hold-off. That's a far cry from the 1.8 that the program offers as a hold.

What the hell am I doing wrong?

 

[caustic]

Re: Rule of 9s (wind holdover)

tag

 

[notquiteright]

Re: Rule of 9s (wind holdover)

I never liked doing math in the field. I use a simple wind card strapped into my range book with fabric rubber bands ( far more sun resistant than regular rubber bands)it also has a milhold chart and comeups for that particualr weapon. The facing page is my range card with generous TRP notations.

Its KISS and it works.

FYI I beleive most call wind holds wind holdOFFS not wind holdOVERS. Over is range where I come from. Then again I dont get out like I used to.

Interesting formulas, but I'd rather work it out in a more comfortable setting without all the added pressure. Cheat sheets arent just for high school algebra anymore.

 

[SierraOne1]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _S2_</div><div class="ubbcode-body">If this has been posted before I apologize, I did some searching and didn't come up with anything.

A few years ago while on a quest to get more training in Iraq on my BRAND NEW M24 (I was a SDM, did the 2 week LRM course...long story), I visited our local friendly ODA compound for some knowledge.

I was shown the light with the Rule of 9's and I was wondering if anybody else has had great success with this or any other "versions" of it that worked out better.

Basically...
Take the wind speed in mph and multiply it by the base number of the range in meters.

Example - <span style="font-weight: bold">3</span> mph @ <span style="font-weight: bold">5</span>00 M = 15

Now each 1/4'd mil is 9, so 1 mil is 36 (9,18,27,36,45,54,etc). Knowing this we take the 15 and figure that it is close to 18 ( 1/2 Mil ). So we say our holdover is going to be light 1/2 hold.

I personally had some good success with it. Anybody have an idea if a similar formula works for the M107 using Mk211? </div></div>

Well, obviously this is not a substitute for going to the range and working it, but on a nasty, blustery day in the comfort of my office, the math definitely checked out on the ShooterReady estimation game. Every wind-call I made was dead-on with the "Rule of 9's."

Thanks for sharing, S2.

 

[BigMahi]

Re: Rule of 9s (wind holdover)

...

 

[Lindy]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What the hell am I doing wrong?</div></div>

It looks to me like the wind hold values you used to derive the constant might have been in MOA, not mils. But whatever you did, that constant value is simply wrong.

If the program calculated 1.8 mils for a 12 mph wind at 500 yards, then the constant should have been (5 * 12) / 1.8 = 33.33

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: notquiteright</div><div class="ubbcode-body">I never liked doing math in the field. I use a simple wind card strapped into my range book with fabric rubber bands ( far more sun resistant than regular rubber bands)it also has a milhold chart and comeups for that particualr weapon. The facing page is my range card with generous TRP notations.

Its KISS and it works.

FYI I beleive most call wind holds wind holdOFFS not wind holdOVERS. Over is range where I come from. Then again I dont get out like I used to.

Interesting formulas, but I'd rather work it out in a more comfortable setting without all the added pressure. Cheat sheets arent just for high school algebra anymore. </div></div>

Yeah, yeah, yeah....

I use a PDA with info tweaked from real world dope, dope cards with data interpolated from real world data tied to my rifle, and other backups.

Having something I can use with any 308 anytime anywhere to get close enough to spot a fast followup from when I have none of that is a tool I will gratefully keep handy.....

 

[notquiteright]

Re: Rule of 9s (wind holdover)

Not sure I understand the point. Getting close enough in 'real world' situations has alot more to do with the lump on the shooter's shoulders than a PDA. I have found the LEAST imporatant variable in my shooting to be the exact wind adjustment, of course alot depends on if you are on a civilian known distance range, or some other venue where you are nicely rested well fed and in little danger of the 'target' deciding he can read wind too!

I am not knocking YOUR use of whatever bell/whistle or voo-doo chant. I have found my misses come from screwed up range guesses, or muffed windspeed calls. My simple card does its part. I guess i just like learning a skill, not a machine.

But hey, to each their own.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

<span style="text-decoration: line-through">You just contradicted yourself, first saying that you'd rather use data cooked up from the comfort of your office....now you are an operator getting shot at??

Reading IS Fundamental my brother, my point is that I will utilize any knowledge I can, becaue no matter how simple I make my dope sheets, I may need to use just my noodle,<span style="font-weight: bold"> not that I use a PDA.</span> This little rule gives me an easy windage call, and elevation is already memorized on major mils for out to 700....about the limit of my range estimation on the fly with my MK I Mod 0 eyeballs.</span>

My apologies for commenting to the wrong poster. The spirit of the PDA comment is intact however-I will use everything I can to interpolate a first round hit, can't have real DOPE for ALL conditions.

 

[Mr Flannel]

Re: Rule of 9s (wind holdover)

I think Sierra 1 was the poster referring to working things out from his office, rather than being outside in marginal weather (fair enough at times!), not NQR.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Priest</div><div class="ubbcode-body">I think Sierra 1 was the poster referring to working things out from his office, rather than being outside in marginal weather (fair enough at times!), not NQR.

</div></div>

OOPS-
My apologies to you NQR.....Reading Is Fundamental, and I F'ed up!

 

[SierraOne1]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">You just contradicted yourself, first saying that you'd rather use data cooked up from the comfort of your office....now you are an operator getting shot at??</div></div>

My office is in my house, dude...and trust me, it's not where I work.

 

[SierraOne1]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What the hell am I doing wrong?</div></div>

It looks to me like the wind hold values you used to derive the constant might have been in MOA, not mils. But whatever you did, that constant value is simply wrong.

If the program calculated 1.8 mils for a 12 mph wind at 500 yards, then the constant should have been (5 * 12) / 1.8 = 33.33

</div></div>

OK, got it. Thanks, Lindy.

 

[sobrbiker883]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SierraOne1</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">You just contradicted yourself, first saying that you'd rather use data cooked up from the comfort of your office....now you are an operator getting shot at??</div></div>

My office is in my house, dude...and trust me, it's not where I work.

</div></div>
Sorry, I need to not post on 4hrs of sleep 29hrs ago.......

 

[SierraOne1]

Re: Rule of 9s (wind holdover)

LOL....no need for apologies, man. I know what you mean...

 

[Sterling Shooter]

Re: Rule of 9s (wind holdover)

I favor for wind using the formula which gets me an answer for wind drift in MOA. I use a constant of 10 no matter what I'm shooting with, or distance I'm shooting to. It's simple, fast, and requires no calculator, pen, or pad. The constant of 10 may not be good enough for a pin wheel X hit, but it's accurate enough for a good hit when I've appraised mid range wind properly. When I have an answer in MOA, I can convert to inches, which my brain can better visualize; and, thereafter, I can favor for a good hit instead of click for it. Some here advocate the same formula which yields an answer in mils. If you have a reticle which is graduated in mils for range estimation, I can understand that by using a formula for wind favors, which yields an answer in mils, the reticle can do double duty. But, with excessive fractions involved for calculations, some may become dependent upon charts, and calculators, as well as pencil and pad; thus, precluding quick hits. In addition, the eye may become too busy chasing or counting line segments, dots or stadia instead of being allowed to remain focused on the reticle/target relationship.

 

[paraiso]

Re: Rule of 9s (wind holdover)

 

[Sterling Shooter]

Re: Rule of 9s (wind holdover)

That's an easy one, to make it doable in my head, I'd take 30 instead of 28. I'd then take 18 minutes or about 9 ft of favor. What I'm saying is you must be able to do it in your head. There are no alternatives. You must do it without any visual/mechanical aids from/at the firing point.

 

[JFComfort]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sterling Shooter</div><div class="ubbcode-body">That's an easy one, to make it doable in my head, I'd take 30 instead of 28. I'd then take 18 minutes or about 9 ft of favor. What I'm saying is you must be able to do it in your head. There are no alternatives. You must do it without any visual/mechanical aids from/at the firing point. </div></div>

Sterling did you get a look at the formula that gave you the windage in MOA? Are the constants correct?

This one;

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mo_Zam_Beek</div><div class="ubbcode-body">This works.

Here is an alternate formula:

Dist in yrds (/10) x Wind Velocity / Constant = MOA of hold

Constants:

0-500 = 15
600 = 14
700 = 13
800 = 12
900 = 11
1k = 10

Therefore looking at the following examples:

350 yrds / 3 MPH = 0.2 MIL
600 yrds / 8 MPH = 0.99 MIL
725 yrds / 15 MPH = 2.44 MIL

Using the 'Rule of 9's' (and converting yrds to meters):

320 meters / 3 MPH = 0.25 MIL
549 meters / 8 MPH = 1.25 MIL
663 meters / 15 MPH = 2.75 MIL


Good luck </div></div>

 

[308RUG]

Re: Rule of 9s (wind holdover)


Dist in yrds (/10) x Wind Velocity / Constant = MOA of hold

Constants:

0-500 = 15
600 = 14
700 = 13
800 = 12
900 = 11
1k = 10

JF Comfort
Great someone else uses it,
I use this formula for F/TR at the moment but haven't had to apply it beyond 1000yrds. Can you tell me if I would be correct in assuming the constants for 1100 and 1200 yards would be 9 and 8 respectively or do these come down further for the drop in velocity.Starting a new shooting class and would be handy to know in advance.
Thanks

 

[Sterling Shooter]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JFComfort</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sterling Shooter</div><div class="ubbcode-body">That's an easy one, to make it doable in my head, I'd take 30 instead of 28. I'd then take 18 minutes or about 9 ft of favor. What I'm saying is you must be able to do it in your head. There are no alternatives. You must do it without any visual/mechanical aids from/at the firing point. </div></div>

Sterling did you get a look at the formula that gave you the windage in MOA? Are the constants correct?

This one;

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mo_Zam_Beek</div><div class="ubbcode-body">This works.

Here is an alternate formula:

Dist in yrds (/10) x Wind Velocity / Constant = MOA of hold

Constants:

0-500 = 15
600 = 14
700 = 13
800 = 12
900 = 11
1k = 10

Therefore looking at the following examples:

350 yrds / 3 MPH = 0.2 MIL
600 yrds / 8 MPH = 0.99 MIL
725 yrds / 15 MPH = 2.44 MIL

Using the 'Rule of 9's' (and converting yrds to meters):

320 meters / 3 MPH = 0.25 MIL
549 meters / 8 MPH = 1.25 MIL
663 meters / 15 MPH = 2.75 MIL


Good luck </div></div>

</div></div>

The SDM class on wind and weather effects presents the formula alluded to above with outcomes in MOA using only the constent of 10, as well as in distance segments which can be multiplied and divided by 10. After all, the formula will likely be used with BDC's and other sighting devices which are graduated in MOA. And, since the M855 or Mk262 round will accept a constant of 10 over their useful trajectory when using a BDC which has been set for a low 300 meter BSZ, the formula works; and, even though 10 is not perfect for most distances, neither will the shooter's wind or distance reading be perfect; but, nevertheless, a good hit inside a heartbeat is the idea, for obvious reasons, and the constant of 10, along with good old MOA, rather than mils, allows for fast, in the head calculations, while eyeball remains on sight.

 

[Lindy]

Re: Rule of 9s (wind holdover)

If you want to know what the wind constants are for any particular load, there is no need to guess. Use a ballistic program set up for your load and a 1 mph full-value crosswind, and work the formula backwards:

<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre>
(range in yards/100)
constant = ----------------------------------
wind hold(mils)
</pre></div></div>

 

[Mr Flannel]

Re: Rule of 9s (wind holdover)

This can be applied with meters also?

 

[Lindy]

Re: Rule of 9s (wind holdover)

Absolutely - assuming the ballistic program is also working in meters.

 

[Mr Flannel]

Re: Rule of 9s (wind holdover)

Thanks mate

 

[Daps!]

Re: Rule of 9s (wind holdover)

great thread.

 

[308RUG]

Re: Rule of 9s (wind holdover)

Thanks Lindy,
Damn mathematics gonna have to get more fingers I think.

 

[TresMon]

Re: Rule of 9s (wind holdover)


Talking maybe more crude yet: anybody use "The Rule of the Square" for short to mid range? I use it for deer hunting when I'm caught off guard.

Say the target is 300 yards... use the first digit of the range (3) and square it:
3x3=9" drift in a 10 mph wind. I can do that FAST in my head, then halve it or quarter (etc.) it for the actual wind velocity really FAST too

400y: 4x4=16" in a 10mph..

450yds: 4.5x4.5=20"

Close enough for guv'ment work on critters out to moderate range with most popular cartridges.

 

[pshell]

Re: Rule of 9s (wind holdover)

Please understand I don't intend to take shots at anybody here, especially the OP.

It's a technique for sure, if you don't have anything else to hold. I was taught this method and used it for some time, but came to realize if I just held what I thought I should hold I had much better luck. As some have pointed out, your actual dope will vary quite a bit. The rule of nine's is for the beginning long range shooter and is taught to beginners. Guys that shoot in quantity will just begin to hold what they see in their telescope. You can't shoot fast enough sometimes, math is slow.
I have found it's better to take an educated guess and be ready with the correct follow on shot than to take none at all. Your situation will dictate that I guess.
Try guessing your hold, you may surprise yourself. The rule of nines is built to show guys what it all looks like and build their confidence to take those long shots. In the world this is taught, an E-type is a big target and a hit is a hit. I'm sure it helps with shooters that can't get enough time behind the gun to get past the PDA's and formulas. Best thing we can all do is shoot our rifles as much as possible in different conditions and terrain.

 

[Sterling Shooter]

Re: Rule of 9s (wind holdover)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pshell</div><div class="ubbcode-body">Please understand I don't intend to take shots at anybody here, especially the OP.

It's a technique for sure, if you don't have anything else to hold. I was taught this method and used it for some time, but came to realize if I just held what I thought I should hold I had much better luck. As some have pointed out, your actual dope will vary quite a bit. The rule of nine's is for the beginning long range shooter and is taught to beginners. Guys that shoot in quantity will just begin to hold what they see in their telescope. You can't shoot fast enough sometimes, math is slow.
I have found it's better to take an educated guess and be ready with the correct follow on shot than to take none at all. Your situation will dictate that I guess.
Try guessing your hold, you may surprise yourself. The rule of nines is built to show guys what it all looks like and build their confidence to take those long shots. In the world this is taught, an E-type is a big target and a hit is a hit. I'm sure it helps with shooters that can't get enough time behind the gun to get past the PDA's and formulas. Best thing we can all do is shoot our rifles as much as possible in different conditions and terrain. </div></div>

You're too kind to the OP and some others here. You also make too much sense while exposing the folly in the "rule" math with mils. There appear to be folks here who just want to role play with their stuff. It's all about their amusement. Perhaps they have the time for math other than on the fly. That's O.K. I guess, it's all good, but, sometimes it's just plain silly.

 

[Mr Flannel]

Re: Rule of 9s (wind holdover)

Take it easy mate. This was a good, collegiate thread until you sounded off. There's a fine line between pointing out reality and coming off as both patronising and condescending. You seem to have enough time to chime in on the maths when it suits you. I don't see anyone here claiming it to be a realistic solution when under a time crunch.

Pshell's point was well taken, and well delivered.