MOA Calculations

[tnichols]

Do you folks have or know of a chart that gives the correct MOA to inches data for scopes. For example: Yesterday I was shooting at 300 yards. My group was approx. 3.5 inches high. At that known distance (300 yards) what would be the correct amount of scope adjustment considering my scope has one quarter MOA adjustments. If this doesn't make sense, I appologize. I just want to shoot a group at a known distance (300 yards on out), look at the center of the group, and then make the correct adjustments to the scope (considering it's one quarter MOA).

Just in case anyone asks, or it makes a difference, the equipment is as follows: Savage 10FP .308 in a McMillan stock, Leupold LR Tactical set at 14X in Badger rings and 20 MOA rail.

[Xfactor]

Do you folks have or know of a chart that gives the correct MOA to inches data for scopes. For example: Yesterday I was shooting at 300 yards. My group was approx. 3.5 inches high. At that known distance (300 yards) what would be the correct amount of scope adjustment considering my scope has one quarter MOA adjustments. If this doesn't make sense, I appologize. I just want to shoot a group at a known distance (300 yards on out), look at the center of the group, and then make the correct adjustments to the scope (considering it's one quarter MOA).

Just in case anyone asks, or it makes a difference, the equipment is as follows: Savage 10FP .308 in a McMillan stock, Leupold LR Tactical set at 14X in Badger rings and 20 MOA rail.

1 MOA (Minute of Angle) is 1/60th of 1 degree of a 360 degree field. At 100 yards, 1 MOA is roughly 1". (To be precise, it's actually 1.047" at 100 yards, but 1" is generally "close enough") Since the angle is constant at any range, 1 MOA is also 1/2" at 50 yards, 2" at 200 yards, 3" at 300 yards, etc.

3.5 inches high at 300 yards is 1.11 MOA... For your scope with 1/4 MOA adjustments, you need 4 clicks down to zero.

(1.11 MOA, rounded to the nearest 1/4 MOA, is 1 MOA... 4 clicks per MOA, so... 1x4 = 4 clicks down)

* Last sentence edited for brain fade - Sorry

Edited September 9, 2009 by Xfactor

[rtr]

MOA stuff can be confusing for me. I tend to just think of 1 MOA as 1" at 100 yards, 2" at 200 yards, 3" at 300 yards, 4" at 400 yards, etc. That tends to make it pretty simple.

[uscbigdawg]

If you're 3.5" high at 300, that's 1 MOA (and change) at 300 yards.

However, your scope correction would be the same as stated above 14 clicks.

It's a bit of semantics of terminology but both answers are arguably correct.

Rich

Edited September 8, 2009 by uscbigdawg

[Dale Rader]

The scope correction would be four clicks, not 14. It is just over one minute off and it is quarter minute clicks.

Dale

[Jack Suber]

The scope correction would be four clicks, not 14. It is just over one minute off and it is quarter minute clicks.

Dale

Thats what I was thinking. 1 click is a 1/4" at 100 yds and 1/2" at 200, right? At least that is how it worked for me Sunday.

[uscbigdawg]

Yep. Took my shoes off instead of just counting on the hands. Sorry.

Rich

[schroed]

for example: (1moa @ 100yd=1.047")

you are 3.5" off at 300 yds

3.5"/1.047=3.34 true moa

3.34/3.00=1.113 moa of adjustment (all moa is based on 100yds ie 3.00*100=300)

1.113/.25=4.452 clicks or 4 or5 clicks (1 click=.25moa)

more Importantly is your leupold: 1" @ 100yd or 1.047" @100yd ??????

edit for 300yds

Edited September 8, 2009 by schroed

[uscbigdawg]

Oooof...let's not get in to true MOA and Shooter's MOA.

Rich

[schroed]

Oooof...let's not get in to true MOA and Shooter's MOA.

Rich

how about mills?

for shooter moa it would be 4.667 clicks----4 or 5 clicks not much difference at 300 yards

[uscbigdawg]

Well the mils for this would be easy (please check my math).

3.5" at 300 yards = .33 mils

Rich

[Dale Rader]

more Importantly is your leupold: 1" @ 100yd or 1.047" @100yd ??????

I think there are very few shooters or rifles that could tell the difference in this.

Dale

Edited September 8, 2009 by Dale Rader

[schroed]

QUOTE (schroed @ Sep 8 2009, 03:38 PM)

more Importantly is your leupold: 1" @ 100yd or 1.047" @100yd ??????

I think there are very few shooters or rifles that could tell the difference in this.

Dale

4.5% error

Dale,

Nice seeing you at the Il. Sectional little wet but lots of fun.

[Dale Rader]

Schroed,

It is always a pleasure to visit with you also; wish we had more free time though.

Your 4.5% error comes out to measuring 1/25th of an inch at 100 yards though. Most shooters, rifles and scopes cannot get that accuracy, let alone the ammo on top of that. A lot of people I have seen measure groups measure to the 1/4 inch and call it good. Once you get out to 300 - 400 yards where you can see a difference, wind starts to come into effect. I am just saying that the scope adjustment is usually much better than the shooter performance especially down to the second decimal point.

Take care my friend,

Dale

[schroed]

Schroed,

It is always a pleasure to visit with you also; wish we had more free time though.

Your 4.5% error comes out to measuring 1/25th of an inch at 100 yards though. Most shooters, rifles and scopes cannot get that accuracy, let alone the ammo on top of that. A lot of people I have seen measure groups measure to the 1/4 inch and call it good. Once you get out to 300 - 400 yards where you can see a difference, wind starts to come into effect. I am just saying that the scope adjustment is usually much better than the shooter performance especially down to the second decimal point.

Take care my friend,

Dale

Dale,

I total agree with you, just my engineering side sometimes gets carried away.

It is easy to carried away with precession I just like to understand what’s going on,

and think that is the big advantage of using mils. There is one thing to remember, if shooting

a .308win at 1000yds vs. 338Lapua at 1000 yards the .308 with such a large adjustment

for elevation you may want to consider the rounding error. But then again I would be using

the .338Lapua because of ballastic numbers.

Regards,

David

Edited September 9, 2009 by schroed

[tnichols]

Thanks for the help guys. I knew Schroed would come through for me. It always helps to have a shooting buddy that's a genius! Now, where do I find a table or graph that gives me this info all the way out to infinity and beyond? I need all the help I can get!

[ChristianHE]

Here's some "fun" if your scope has a mildot reticle, you can hold over instead of clicking if you want to...

Like said above, 1 MOA at 100 is 1 inch, 2 inches at 200, 3 inches at 300 etc.

Say you're shooting at 400 yards and you're 30 inches low (according to data from your ballistics calculator like http://www.hornady.com/ballistics/ballistics_calculator.php or you have a biiiiigg target )

at 400 yds 1 MOA is about 4 inches, so 30 divided by 4 = 7.5

MOA to MIL conversion factor is 3.438, so 7.5 divided by 3.438 = 2.18

Just hold the 2nd MilDot that's below the crosshairs just above your target and pop it!

1 Milliradian is 36" at 1000 yds so it's 3.6" at 100 yds (1/10th), 7.2" at 200 yds, 10.8" at 300, 14.4" at 400. So two dots is 28.8" at 400 yds.

If I blew some math, hey, I program all day, brain is fried! But you get the idea, Google it.

[GusthotGriz]

Do MOA scopes use 1” or 1.047” as the basis for 1 MOA?  I just ran the numbers, and if I am correct at 1500 yards the difference would be more than 14”.  Am I missing something obvious?

[IVC]

14 years later... but here it goes. 
 

MOA is a minute of angle. There is no 1" or 1.047" or anything of the sort that would be "basis" for MOA. What you can do is calculate how much arc 1 MOA covers at any distance. Since these arcs are extremely flat (for minimal angles involved in sighting in), both MOA and MIL calculations treat them as just flat distances. 
 

But back to MOA. There are 360 x 60 minutes of angle in a full circle. At any radius R, this angle covers 2 x R x Pi arc (full circumference in this case). So, if you want to know how much a MOA covers, you divide the arc by the minutes: (2 x R x Pi) / (60 x 360). If you measure R in *hundred* yards, it's quite convenient to simplify the equation since 1 yard = 36 inches. You end up with (2 x N x 100 x 36 x Pi)/(6 x 36 x 100), cancel out  the 3600 and it's just N x Pi/3. 
 

At 100 yards, N = 1 and 1 MOA covers arc of Pi/3 = 1.0472". At 1500 yards, 1 MOA covers 15 x Pi/3 = 15.708". Note that the angle of 1 MOA doesn't change, what changes is the length of the arc at different distances. 
 

So, at 1500 yards, your one click at 1/4 MOA would result in adjustment of 15.708"/4 or roughly 4". 

[outerlimits]

22 minutes ago, IVC said:

14 years later... but here it goes. 
 

MOA is a minute of angle. There is no 1" or 1.047" or anything of the sort that would be "basis" for MOA. What you can do is calculate how much arc 1 MOA covers at any distance. Since these arcs are extremely flat (for minimal angles involved in sighting in), both MOA and MIL calculations treat them as just flat distances. 
 

But back to MOA. There are 360 x 60 minutes of angle in a full circle. At any radius R, this angle covers 2 x R x Pi arc (full circumference in this case). So, if you want to know how much a MOA covers, you divide the arc by the minutes: (2 x R x Pi) / (60 x 360). If you measure R in *hundred* yards, it's quite convenient to simplify the equation since 1 yard = 36 inches. You end up with (2 x N x 100 x 36 x Pi)/(6 x 36 x 100), cancel out  the 3600 and it's just N x Pi/3. 
 

At 100 yards, N = 1 and 1 MOA covers arc of Pi/3 = 1.0472". At 1500 yards, 1 MOA covers 15 x Pi/3 = 15.708". Note that the angle of 1 MOA doesn't change, what changes is the length of the arc at different distances. 
 

So, at 1500 yards, your one click at 1/4 MOA would result in adjustment of 15.708"/4 or roughly 4". 

you lost me after "14 years later"...:)

[SnipTheDog]

4DOF and your optics provider will have a web app that will tell you what your calculated drops are.  Arken has a ballistic table that will tell me drops out to 1500 yards in MOA for us poors.

[GusthotGriz]

You folks are awesome.  Exactly the information I needed.  I was an iron sights sharpshooter in the Army, specializing in 300 meter shootouts.  I also do SASS.  But have always wanted to try my hand at 1000 yd plus, but scopes are totally new to me…except the little 3x tasco I had on my first WesternAuto  .22 LR in 1966.  Yeah, it’s been a while.  My original question about 1” vs 1.047” came from the whole “MOA is 1” at 100 yards” thing.   Being a bit nerdy I did a spread sheet out to 1500 yards, but then ran across an article that said an MOA is actually 1.047”, so I adjusted the spreadsheet and saw a significant difference at 1500 yards.  Then that got me wondering how modern scopes ((Arken EP5 specifically) were calibrated.  I sent an inquiry to Arken with the same question but got no reply.  Probably thought “this guy is too dumb to be using firearms.  Maybe if we ignore him he’ll go away”.  Anyway, thanks for taking me seriously.  See you at the range.