MOA and Scope Adjusting For Dummies...


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Still 2 Many Choices!?
June 6, 2008, 04:30 PM
Let me begin by saying I am no dummy, yet lacking when it comes to understanding MOA. If my scope is calibrated for 1/8" adjustments at 100 yards, what is the adjustment doing at 25 yards? Is it 1/16", or 1/32" at 25 yards? Once I finally get out to 200 yards, what will the adjustment do then? Will the 1/8" click turn into a 1/4" for every click?

Basically, is there a simpler way to figure out all this MOA adjustment especially at odd ranges, like say 75 yards, or 250 yards for example.

My FAL is sending thanx in advance.

Still 2 Many Choices!?

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hps1
June 6, 2008, 04:58 PM
If my scope is calibrated for 1/8" adjustments at 100 yards, what is the adjustment doing at 25 yards? Is it 1/16", or 1/32" at 25 yards? Once I finally get out to 200 yards, what will the adjustment do then?

1 MOA = 1" for each 100 yards (for all paractical purposes). If you have 1/8" MOA clicks, 1 click moves POI 1/32" @ 25 yds, 1/16" @ 50, 1/8" @ 100 and 1/4" @ 200 yds. Another way to put it would be full value @ 100, 1/4 value @ 25, 1/2 value @ 50 and 2x value @ 200.

Regards,
hps

Tarvis
June 6, 2008, 05:57 PM
hps1 got it right on the nose. To take the definition further: MOA is a measurement of the angle, while inches are referring to distance at the POI.

Quiz time for Choices: if you adjust your scope 1.5 Minutes Of Angle, how far will it shift the Point Of Impact at 800 yards and how many clicks would that be? And no answer blurting, this one is for Still 2 Many Choices!?

Omnivore
June 6, 2008, 10:26 PM
Yup, that's why we learned multiplication and division back in primary school-- to adjust our rifle scopes!

Hps1 and Tarvis nailed it. Lets back up a bit and define the term:

One minute of angle (or arc) is one sixtieth of a degree, or one 21,600th of a full circle (360 x 60). As it happens, it's roughly equal to one inch at 100 yards. You can do that math too--radius of 100 yards = circumference of 628.318 yards (2 pi R) or 22,619.46 inches. Divide by 21,600 and you get 1.047 inches. It doesn't take much looking at the numbers to see that if you double the radius (your shooting distance) you double the value of that minute.

People who actually know math could simplify that do doubt.

There are courses in precision marksmanship offered around the country. A good one will deal with all this and much more. Go to Boomershoot.org and look up the rifle clinic, for one example. That guy's good. He's good with people, and has a lot of experience teaching. The NRA would be another good source of info on classes. G. David Tubb wrote a good book called "Highpower" and Plaster has a book called "The Ultimate Sniper". Both worth reading.

Bwana John
June 6, 2008, 11:13 PM
Real men use radians.:eek:

Still Too Many Choices!?
January 20, 2009, 11:06 AM
Whoops, I kinda forgot about this one. Hope these answers are correct. Let's see Tarvis, I think the POI will shift 12"@800 yds if I adjust the scope 1.5MOA, and that would be 12 clicksof adjustment@800 yards:).
Someone please let me know if this is correct.

Still 2 Many Choices!?

1858
January 20, 2009, 01:50 PM
Quiz time for Choices: if you adjust your scope 1.5 Minutes Of Angle, how far will it shift the Point Of Impact at 800 yards and how many clicks would that be? And no answer blurting, this one is for Still 2 Many Choices!?

Tarvis, that's a misleading question for beginners. Adjusting the scope 1.5 MOA will change the POINT OF AIM by 12" but not the POI unless you have the flattest shooting round in history!! A more "realistic" example would be ...

Based on muzzle velocity, bullet weight, BC, temperature, humidity, elevation, a 200 yard zero and zero wind value, a reference table tells you that your bullet will drop 148" at 800 yards. What adjustment do you need to make on your scope to get on target.

:)

WNTFW
January 20, 2009, 06:27 PM
It can be counter intuitive for some people. Just be glad 1 MOA is close to 1" @100yds.

Still Too Many Choices!?
January 21, 2009, 01:16 AM
Using my 1/8 MOA scope as the example, I guess that would be 9 clicks up :uhoh:....

Still 2 Many Choices!?

1858
January 21, 2009, 03:17 AM
Using my 1/8 MOA scope as the example, I guess that would be 9 clicks up

The correct answer to the question in my previous post is 17.67 MOA which on your scope with 1/8 MOA "clicks" would be 141 clicks up which would give you 17.63 MOA so you'd be a tad low. 142 clicks up would put you at 17.75 MOA ... a tad high.

Here's the math:

At 100 yards, 1 MOA = 1.047"

At 800 yards, 1 MOA = 8.376"

148"/8.376" = 17.67 MOA

17.67 MOA/0.125 MOA = 141.4 clicks


Try this calculation using 1 MOA = 1.0" at 100 yards and 8.0" at 800 yards and see how far off you are ...

What MOA adjustment do you get from one turn of your elevation dial on your 1/8 MOA scope? My Mark 4 with M1 dials is 15 MOA per turn.

:)

Still Too Many Choices!?
January 21, 2009, 09:28 AM
Thnx... And holy crap, was I off! Hopefully I can get a handle on this one day.

Still 2 Many Choices!?(and less confused now:))

lions
January 21, 2009, 01:51 PM
If you cut the distance in half, you have to double the number of clicks to move 1/8".

to move 1/8" @ 100yds= 1 click
to move 1/8" @ 50yds=2 clicks
to move 1/8" @ 25yds=4 clicks

If you double the distance, you double how far each click moves POI. (Same goes for tripling)

1 click @ 200yds= 1/4"
1 click @ 300yds= 3/8"
1 click @ 400yds= 1/2"

Hope this helps, this is the easiest way for me to remember.

lions
January 21, 2009, 02:01 PM
1858
your bullet will drop 148" at 800 yards. What adjustment do you need to make on your scope to get on target.

Try this calculation using 1 MOA = 1.0" at 100 yards and 8.0" at 800 yards and see how far off you are ...

Using my method,(posted above)8x the distance so 8x1/8"=1"

1 click @ 800yds=1"

So my answer would have been 148 clicks. Your answer was 141 clicks, so by rounding 1 MOA to 1" I would be shooting ~7" high at 800yds.

I guess now all we have to figure out is, at 800yds, is 7" close enough?

For me, the answer is yes.

ETA:And I didn't have to use a calculator!:neener:

Funderb
January 21, 2009, 02:16 PM
Real men use radians

only if you are using real minutes!

LKB3rd
January 21, 2009, 02:26 PM
Also consider this. For a .308, you'll have the same setting for 200 yards, and somewhere in the 25-30 yards range. That setting will be around 3 inches high at 100 yards. How can this be? The sight line is slightly above the line of the barrel. So, when you shoot 200 yards, the bullet starts at an upward angle, passes that sight line on the way up at 25-30 yards, passes 100 yards around 3 inches high, and starts back down and hits the point of aim at 200.
Sort of off track, but I was thinking you might get confused if you tried to lower your point of impact from 100 yard settings down to 50 or 25, when you actually raise the rear sight to hit closer than 100 yards, if starting at 100.

1858
January 21, 2009, 02:29 PM
I guess now all we have to figure out is, at 800yds, is 7" close enough?

For me, the answer is yes.

Good question ... for some yes, for others, maybe not. But this is a good example of the "practical" difference between 1 MOA = 1.000" and 1.047" and a "real world" scope adjustment. It's better to make an informed decision right?

:)

1858
January 21, 2009, 04:04 PM
Real men use radians.

MOA is derived using radians ... S = r*theta (in radians) ... C = 2*PI (radians)*r is a specific case to calculate the circumference of a circle.

:)

Brian41
January 21, 2009, 04:47 PM
my head hurts.....

I think i'm gonna go shoot stuff

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