Formula for MOA and tacticle scopes

J

Jason_Schmidt

New member
I while back I read somewhere where a guy explained an easy and fast formula for figuring how many clicks you need for the different ranges with the tactical style scopes.

I knw what MOA is but the formula this guy had for this was really cool.

I hope y'all know what I mean cause this is a hard question to explain.

Say my gun is sighted dead on @100 yards........

bullet drop @ 1000 yards is 380"

with a 1/4 click scope,how many clicks would it take for it to hit dead on @ 1000 yards?

OK,I am now cross-eyed anyone else? /ubbthreads/images/graemlins/smiliesmack.gif
 
It's just simple arithmetic. A 380" drop at 1000 is 38 MOA which with a 1/4 MOA click scope will take 4 times 38 clicks. 4 times 38 is 152 clicks. That is more movement than most scopes can do from centered. Most scopes can do it if mounted on tapered bases so the 100 yard zero is near the bottom of the vertical adjustment.

Jack
 
Remember it's not just 1/4" it's 1/4 inch per hundred yards (IPHY), so 4 of them would be 1" @ 100 yds. If the clicks are .25 MOA then again multiply IPHY value by 1.05, then your 4 .25 MOA clicks is 1.0 IPHY x 1.05 or 1.05 inches @ 100 yds.

1 MOA is slightly bigger than 1 IPHY or IOA.

U have to study this stuff a bit to be able to pick it up quickly. I've found it's important to memorize 2 conversions--

1 MOA= 1.05 IPHY (IOA), and

for mil-dots--

1 dot to dot subtension= 3.6 IPHY, or 3.4 MOA

When u looke through your scope, start trying to view the reticle as an angular system of measurement if there's more than 1 point of reference in it-- same for your clicks.
 
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While we're on the subject of mildots.. I have a Meuller tactical... 416X50... how can I use those little dots in the scope? I'm shooting a 250 and the bullets are 50gr, travelling at 3900fps.. and 1.6inches high at 100. How would that work? Especially the elevation ones.. the next one down would be what? say at where I need to use it. lol
 
Jason, go to Varmint Al's website and there is a formula on there. It's actually in the form a of program. You input all your info and it spits out a little document you can print and tape to your rifle. Works AWESOME. it is not just a plug and chug formula. You have to input info about your scope and the MOA clicks.
 
as it applies to artillery measurements........Dictionary of International measurements definition :

mil [2]
a unit of angle measure, used in the military for artillery settings. During World War II the U. S. Army often used a mil equal to 1/1000 of a right angle, 0.1 grad, 0.09°, or 5.4 arcminutes (often written 5.4 moa; see "moa" below). More recently, various NATO armies have used a mil equal to 1/1600 right angle, or 0.05625° (3.375 moa). In target shooting, the mil is often understood to mean 0.001 radian or 1 milliradian, which is about 0.0573° or 3.43775 moa. In Britain, the term angular mil generally refers to the milliradian. 1 milliradian corresponds to a target size of 10 millimeters at a range of 10 meters, or 3.6 inches at 100 yards.
 
OK,..you are getting confused by trying to do too much math.

first,..a 1/4" scope will have these values

1/4" @100
1/2" @200
3/4" @300
1" @400
1 1/4" @500
and so on until you reach 2 1/2" per click at 1000yds.

The problem with using inches of drop in the field is that it causes a calculation to have to be made. You have to divide 380" by 2.5" clicks (value at 1000yds) to come up with 152 clicks of come up for a 1000yd sighter.

The thing I prefer with using MOA, is that it takes into consideration BOTH linear measurements, the line of sight AND the arc of the bullet. The inches method only takes into consideration the arc with a click value needing to be applied and then a division made to get your come-ups.

Now lets run the question again with MOA.

I am dead on at 100yds,...and I want my comeups for 1000yd sighters to get started (you are never exactly where the chart says you will be, you'll be a click or three away). so,..ifin the chart you run says you need 380" at 1000yds,..then you change that to 38MOA [(380/10), due to the fact that your distance has increased by a multiple of 10,..(100yds x 10 = 1000yds). Therefore, you need 38MOA of come-ups,..sooooooooooooooooooooooo

if your clicks are 1/4moa,..then 38moa would require 38 x 4 = 152 clicks. Because it takes 4 clicks to make one MOA, so it takes 4x 38moa to make 38moa, or 152 clicks.

the MOA is easier,..if your chart is run in MOA increments. You simply check your come-ups on the chart in MOA, and divide that by 1/4moa clicks.

lets run another one

lets say I need 9moa to make 600yds from my zero. I know my NXS knobs to be true 1/4moa clicks. Soooooo, for 9moa I need (4x9) or 36clicks. No calculation other than counting clicks.

One other trick I use is to count my clicks like this; (this is how I do it so I DO NOT have to make calcualtions in the field) /ubbthreads/images/graemlins/grinning-smiley-003.gif

one, two, three, ONE (1moa)
one, two, three, TWO (2moa) etc etc
one, two, three, THREE
one, two, three, FOUR
and so on. As I hit the fourth click, I have my mental note of just how many MOA's I have adjusted in/out, left/right. Then reverse the direction and count the same way and even blindfolded, you will be back at your original zero. /ubbthreads/images/graemlins/ooo.gif

clear as mud?
 
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Like others have said, I like the minutes and drop chart over mildot math! I have a mildot scope but dont even use it, for me its way to much to even think about.

Also not mentioned above, I dont think but will throw it in anyways!

Using any of the above mentioned methods, you should start from a base line zero at 100 yards, meaning your sighted in zero at 100 and not high, or you will be doing even more math, adding subtraction to the equation
 
I 'think' the mil dot system is supposed to be used to estimate range to target, not estimate holdover like a leupold Boone and crockett reticle.

If you know Gen Sanchez is 6ft tall, and you know how big your "mil" is at 10power, you can put the general against your reticle and count the dots, do the math, figure the range, dial in the clicks (you have to figure this out at the range or chrono it and run a program) and hold the cross hairs right on.
 
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As Furhunter stated, your chart "zero" HAS TO agree with your real "zero". If you are 2" high at 100, then you keep inserting new "zero" ranges and re-running the chart until the chart states that you will be 2" high at 100yds, just as you really are, then all corresponding MOA values are now back in line with no calculations. Until you get the hang of it, it is still best to sight dead on at an interval in some form of 100yds. If you use a 20MOA base to gain extra elevation in the scope, you may not be able to get on at 100yds, you may be some amount above the bullseye, even when adjusted to the bottom of the adjustments. You DO NOT want to adjust your scope all the way in any direction as this can and will cause them to act erraticaly. Try to keep them closer to 3/4 total travel if you can.

I have a 6.5-06AI that was 20" high at 100yds with a 20MOA base and the scope dialed all the way down. Now, I put on a 10MOA base and came a few MOA off the bottom of the scope adjustemtns and am right at 10"+/- high at 100yds. So, to find MY zero, I will have to shoot this thing out to around 500-600yds,....or I can simply change the zero range in the chart until it states that my bullet will be 10" high at 100yds, and I can print and use that chart, it will tell me pretty accurately what MY zero is. But it will also tell me how much HOLD-UNDER I will need for the distances out to the zero range and the holdover after my true "zero" range.

Confused yet?

use the JBM balistics calculator and input all your data and run the chart. Then,..change your zero range and recalculate it again,..the chart will automaticaly adjust the come-ups to correspond to the new zero. Compare the charts to one another, and you will see the trajectory hasn't changed,..just the values DEPENDING on the zero range, which are the come-ups.

so,,if you run it at zero at 100yds, then it will give a value of (0) for your 100yd MOA column, now change the zero to say 400yds and run it again. You will notice that the figures for come-ups change to correlate to the trajectory of that load/bullet/BC/MV etc as if it were dead on at 400yds. Now your 100yd come-up MOA column will read some (+xxx value). The positive means you hold UNDER by that much MOA( in laymens terms,..you will be +xxmoa high), and the -xxx values means you hold over or "come-up" that amount of MOA for the given distance(because you will be XXmoa low). The trajectory figures are basically the same, the zero range is all that has been changed. NOW, THE AMOUNT THE ZERO HAS CHANGED BY WHEN YOU WENT FROM 100 TO 400YD ZERO, WILL BE REDUCED FROM YOUR ORIGINAL CHART'S 1000YD COME-UP BY THE SAME AMOUNT, AND THE 100YD MOA COLUMN WILL NOW SHOW THE REMAINDER OF THE AMOUNT, BUT DISPLAYED AS HOLD-UNDER INSTEAD OF THE (0) VALUE FROM THE FIRST CHART.

so say before your zero was 100yds and you needed the 38moa to get to 1000yds. Now the second chart showing lets say a zero at the 400 you inputed, will show (these are NOT real figures, just examples) say a hold-under of say 5MOA at 100yds and a holdover of 33MOA at 1000yds. SEE, the trajectory of 38MOA is still there, it's just where along the chart you want your POI to correspond to your POA. (your "zero")

how's yer head now /ubbthreads/images/graemlins/smiliesmack.gif /ubbthreads/images/graemlins/confused1.gif /ubbthreads/images/graemlins/grinning-smiley-006.gif
 
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JustC

Great posts!! Glad you did it not me! thats alot a splainin' ta do /ubbthreads/images/graemlins/laugh.gif
I'll tell ya if I didnt understand it already, my brain would be scrambled eggs right now /ubbthreads/images/graemlins/smile.gif

Funny thing is.
If all this confuses anybody, your not alone but once you get it, its easy!!! its one of those all of the sudden the light comes on thing!!
 
computer-sign-bangin-head-ani.gif


I feel like someone put my head in the microwave!! /ubbthreads/images/graemlins/smiliesmack.gif

I really aprecciate the help fella's,but I'm gonna have to print this thread and study it /ubbthreads/images/graemlins/grin.gif I am starting to kinda understand how it is better to think of it as MOA instead of inches of drop.I will study your post's some more then like y'all said the light will come on and I will understamd it.

Thanks again for the help,I know it was work just trying to exolain it /ubbthreads/images/graemlins/grinning-smiley-003.gif
 
Trying to remember all those clicks is not the way to go. It is much better to do it in inches like we do. Take a 100 yd zero and figure out how many inches you have to come up to hit your target at the different distances out to 1000 yds. The problem is you will have to actually shoot it after you get close to know for sure what the come ups really are with your rifle/load.

It is much easier to remember the inches instead of the clicks. For example, turn the dial on my Leupould 30mm LR Target optic 10 1/2 inches up to be dead on at 500 yds. Much easier and quicker than trying to remember that many clicks.

However on the windage, you must remember the formula as stated above.

1/4=100
1/2=200
3/4=300
1" =400
and so on.

No matter what, you are gonna have to shoot your rifle to learn for sure.
 
Take a look at your tgt. knob-- is it calibrated in IPHY, or MOA?? Chances are it's not gonna be perfectly calibrated anyway, so this is 1 of the resons you'll have to shoot it to find out either just what your zeros are at the various ranges, and/or the "exact" click value of your scope. More importantly though the turret should be repeatable such that the clicks are the same throughout most of the adjustment range.

Learn the conversions--it's not hard, and you'll be better versed to understand how it all fits together.

When it comes to ballistic/ranging reticles, a ballistic reticle is a ranging reticle, and vice versa. That mil-dot can be very easily applied as a ballistic reticle. It's just a "repeating interval" ballistic reticle, if u will. Think about it, why do most people buy a mil-dot scope. R they gonna range with it?? I'd bet less than 30% of guys that buy mil-dot reticles in their scopes have any idea how to use it-- but it looks cool, so why not impress their buddies? Learn to use that reticle as a ballistic reticle-- you'll be using it more for that application than what it was designed for-- believe me. Run the ballistics program, and calculate the drop chart in MOA then find at what range:

1st dot-3.4MOA
2nd dot-6.8 MOA, etc.

...is zeroed for. That'll get u started. Do the same for windage. If u have any mathematical skills at all u'll figure out how to manipulate the data/scope for your uses. If that Mueller has an accurate turret, then another great application for the mil-dot is "tactical" windage holdoff. This way u can run the clicks, and apply the dots for windage more directly-- this is a fantastic application of the mil-dot reticle IMO.

Ballistic reticles are simply reticles that are supposed to come close to zeroing at even 25/50 or 100 yd. intervals such that interpolation is easier-- but i've never seen one yet that's "perfect", and zeros r gonna change with changes in meteorological conditions anyway, sometimes significantly beyond 5 or 600 yds.

Burris website is a great place to get info on ballistic reticle applications. Here's my favorite--

www.ottllc.com/specialtypistols/sp20.pdf
 
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I must be incredibly stupid, trying to use a mildot to estimate range, leaves me losing all the will to live. I use a range finder, and know where my guns shoot every hundred yards out to 400, which is far enough for me.
 
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I must be incredibly stupid, trying to use a mildot to estimate range, leaves me losing all the will to live. I use a range finder, and know where my guns shoot every hundred yards out to 400, which is far enough for me.



A laser range finder is usually going to be your primary ranging device anyway. You can range trees and rocks and fence posts and stock tanks to get base line yardages and then decide how far it is to your target based on those known landmarks, at least most of the time.

The best single use for mil dot scopes is for hold overs. You have a base zero, which is the main crosshair zero. Then you get zeros at additional yardages based on the mil marks. This lets you shoot way out there without needing to adjust the scope unless you have a heavy cross wind.
For Instance:
I do a little diagram that goes on the inside of my scope cover cap. Whenever I pop the cap open it sets right up there to give me a visual reference for various yardages.
Can't make a decent picture in a note but it looks just like what you would see when looking thru the scope. A picture of the mil reticle with all the dots. On the diagram I have a horizontal line to indicate that I would hold over
1/2 MIL for a 200 yard shot
1 1/8 MIL for a 300 yard shot
2 1/8 MIL for a 400 yard shot
3 1/8 MIL for a 500 yard shot
4 1/4 MIL for a 600 yard shot
 
Here is the piece I wrote a while back on MOA reticles...

http://practicalrifler.6.forumer.com/viewtopic.php?t=139

Bottom line is this: When it comes to ranging a target of known size with the reticle... If you think in inches and yards, the MOA reticle is the better choice. If you think in centimeters and meters, the mildot reticle is more user friendly.

The easiest thing for most folks to do is to print out a bullet drop chart, in 25 yard increments, to the max distance you will be shooting. Out from each yardage value, put the number of MOA it takes to go to that range. For example, it's 15.2 MOA to 600 yards (from you 100 yard zero) you simply dial in 15.2 MOA--or 15 MOA plus one 1/4 MOA click (which is actually 15.25 MOA but that's close enough). If your scope uses 1/8th MOA clicks, you still just watch the hash marks on the turret and dial in 15 MOA, plus two more clicks.

You don't have to count clicks like "one, two, three, four...thirty seven, thirty eight," etc. Just go by the MOA hash marks on the target turret...

For the windage, it is much easier to do this. (By the way, this was taught to me by a tactical shooting instructor, who is also a retired 'Nam era sniper). Figure your wind drift in INCHES--not MOA. Run a ballistics program and input a 1 mph wind, rather than the traditional 10 mph value.

By knowing how many INCHES the bullet will move in a 1 mph wind, all you have to do is figure the full value of the wind and multiply that by the number on your drop chart. If your bullet moves 2 inches for each mile per hour of wind at 500 yards, and the wind is blowing at 8 mph, then multiply 8 by 2 which gives you 16 inches of drift.

Then, if the wind value was not full value, reduce the final figure by the proper amount (example, a half value wind will not move the bullet 16 inches, but rather 8 inches).

Most of us will use hold off to allow for wind. That's why it makes more sense to calculate the wind drift in inches, rather than MOA. (If you want to convert the inches to MOA it's an easy matter; 16 inches at 500 yards is a little over 3 MOA).

Dan
 


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