What is MOA?

[ar15barrels]

In the Marine Corps I learned clicks. Adjusting clicks up or down and right or left.

The clicks had a "value" to them.
Probably 1/2 moa per click.

So, say you needed to adjust 4 clicks to zero the gun.
That was a 2 moa adjustment.

[someoneeasy]

The clicks had a "value" to them.
Probably 1/2 moa per click.

So, say you needed to adjust 4 clicks to zero the gun.
That was a 2 moa adjustment.

The clicks did have values, for windage at 200 yards, 1 click = 1" at 200 yards and 1 click = 2 1/2" at 500 yards i forget what 300 yards was.

[michaelthetrojan]

OK, I have to ask, shouldn't a Lance Corporal in the Marine Corp. know what MOA is?
I am seriously not trying to be a smart a**, but isn't this covered in a Marines basic rifle training?

not a chance... lol Drill instructors dont care how it is done as long as it gets done

[ar15barrels]

The clicks did have values, for windage at 200 yards, 1 click = 1" at 200 yards and 1 click = 2 1/2" at 500 yards i forget what 300 yards was.

Those ARE 1/2 moa clicks.
300yd clicks would be 1.5" on target.

[Renaissance Redneck]

(Snipers use 'mils')

Yes that's true, but they are taught about MOA. They do have an understanding of the concept.

FYI, my son is a USMC Scout/Sniper. I'll ask him more about any MOA discussions in sniper school later when I see him.

EDIT - I seem to remember my son saying something odd about the Leupold scope used on the Army's M24. If I remember correctly, he said that the scope is set up a bit goofy; the reticle in graduated in mils, and the click adjustments in MOA. I'll try to confirm this.

[postal]

maybe off topic, but that kinda raises an interesting question for me. if I sight in a scoped rifle, let's say at 100yds, if someone else shoots that rifle, theoretically the crosshair on the target at 100 should be the same, depending of course on shooter skill, etc.

why wouldn't the same hold true for irons? I imagine a six oclock hold versus center target hold, but theoretically, wouldn't the same sight picture (which is supposed to be the same) with an aperture/mil post set up, like on my garand, be the same POI regardless the shooter?

I get mechanical zero versus sighting in. I've done that. but once set, the sight picture is done right is the sight picture either way. what would be different regarding irons? and I'm asking out of lack of knowledge and out of curiosity.

You have it exactly backwards.

If you zero a rifle scope at 100yd, another person can shoot that rifle, and not be exactly on target because the shape of their face/cheekbone gives them a different cheekweld than you. So their eye is in a different position on the stock compared to you.

With a scope, there are only 3 points of reference. Your eye, the crosshair, and the target. If your eye is in a different spot, the crosshair and target line up differently.

With Irons, there are 4 reference points. Your eye, the rear sight, the front sight and the target. Everyone will shoot iron sights with no change in impact point assuming they know how to shoot... You cant have your eye in the wrong spot like with a scope, because you have to align the front and rear sight.

So with Irons, the only variable is shooter skill, and what sight picture the person is used too- such as 6 oclock hold or top of sights on center of target- that kind of thing.

[Kolo589]

Yes that's true, but they are taught about MOA. They do have an understanding of the concept.

FYI, my son is a USMC Scout/Sniper. I'll ask him more about any MOA discussions in sniper school later when I see him.

EDIT - I seem to remember my son saying something odd about the Leupold scope used on the Army's M24. If I remember correctly, he said that the scope is set up a bit goofy; the reticle in graduated in mils, and the click adjustments in MOA. I'll try to confirm this.

That's actually pretty common in a lot of scopes. You can get a Mil-Dot reticle (which is typically the standard) but your adjustment turrets can be either MOA or Mil depending on brand of scope and how it's set up. Leupold typically will have their M1 turrets for both elevation and windage which are, IIRC, 1/4 MOA clicks, but you can also get their M5 turrets installed which are .1 mil per click.

Some companies have Mil-Mil setups by default and a few offer MOA-MOA setups as well. The key part is knowing what your reticle units are and what your turret units are. You can mix and match everything and it's all just a bit of math.

[Kolo589]

You have it exactly backwards.

If you zero a rifle scope at 100yd, another person can shoot that rifle, and not be exactly on target because the shape of their face/cheekbone gives them a different cheekweld than you. So their eye is in a different position on the stock compared to you.

With a scope, there are only 3 points of reference. Your eye, the crosshair, and the target. If your eye is in a different spot, the crosshair and target line up differently.

With Irons, there are 4 reference points. Your eye, the rear sight, the front sight and the target. Everyone will shoot iron sights with no change in impact point assuming they know how to shoot... You cant have your eye in the wrong spot like with a scope, because you have to align the front and rear sight.

So with Irons, the only variable is shooter skill, and what sight picture the person is used too- such as 6 oclock hold or top of sights on center of target- that kind of thing.

It's my understanding, and I could be totally wrong but, if you properly remove the parallax from the scope (ie you adjust it so you can shift your head and not have the reticle move off target) then your eye position isn't a limiting factor for accuracy. Granted, proper eye relief and cheekwelds are good just for consistency's sake and allow for other things like proper positioning behind the rifle and not applying other irregular forces that could throw off a long distance shot, but with proper parallax adjustment your eye should be able to travel anywhere in relation to the scope's axis and not have the reticle move in relation to the target.

[postal]

I dont have a technical answer for that, but I do not believe it's correct.

The parallax adjustment would allow the person who ZEROed the scope to be in a better position though.

Think about it a second.....
Your eye, an object in space (the reticle) aligning to the target.

Look at a small object near you. And the object or spot on a wall across the room behind it.

Shuffle to the left or right. And look at the small object, and whats behind it...

The object, (substitute for a reticle) never moved, but your eye did. And whats lined up behind the object has shifted.

In my case, sitting in the living room.... looking at the little 'fob' on the chain of the ceiling fan, and the spot on the ceiling behind it. Move my head to one side.... the spot on the cieling behind it moves too. Imagine, that fob was the reticle of a rifle scope- bagged in solid position that doesnt move. That shift in eye placement shifts the target you see.

Even setting parallax this will happen. It will significantly reduce the error, but there is still error induced from it.

This is the reason why proper/REPEATABLE cheekweld is critical when using a scope. Its only your eye- which can move- and the reticle a fixed object.... only 2 points of reference drawing a direct line to the target.

With irons, the front and rear sight HAVE to be lined up, which eliminates eye placement/cheekweld as a variable.

So.... because the shape and size/shape of peoples heads/cheek/ cheekbone are different, a scoped rifle MUST be zero'd for 1 shooter. With that variable of eye placement, it wont zero for a lot of other people. Though, they will be VERY CLOSE, it wont be perfect.

Kind of the same with a shotgun with a bead front sight. Only 1 point of reference and your eye- if you shift to one side, you'll be aiming off. Though a shotgun is usually easy to aim because you should be looking straight down the barrel at the bead.

[Pthfndr]

With irons, the front and rear sight HAVE to be lined up, which eliminates eye placement/cheekweld as a variable.

The part in bold is totally wrong. It is every bit as critical as it is with a scope. Just ask anyone who shoots High Power or Palma. Having your eye closer or farther away from the rear sight will cause vertical stringing. Off to the side slightly causes those unknown fliers.

Doesn't matter if it's a service rifle (an AR15) or a rifle with aperture sights. On a match rifle or Palma rifle large adjustments for elevation are made with the front sight, not the rear, so as to minimize the change in relationship between the rear sight and the shooters eye since it's easier to adjust the front sight than it is to adjust the cheek rest.

I shoot all and speak from experience. Not just something I read on the internet (not saying that's where you got your info).

because the shape and size/shape of peoples heads/cheek/ cheekbone are different, a scoped rifle MUST be zero'd for 1 shooter.

The same holds true for iron sights.

[postal]

I'll take your word for it. I know who you are.

Thinking about it.... what you say about vertical stringing doesnt make sense to me.... I dont get how closer or farther to the sight would change elevation.

But- thinking about cheekweld that you said, does make sense... since if you moved to one side, it would induce a parallax error (for lack of a better term) Thinking about that, I know it's true, though my first thought which I posted, was that it was eliminated with 2 reference points instead of 1. But- I see my assumption was wrong.

Can you explain in detail how closer or farther to the sight changes elevation?

[SoldierLife7]

I thought it stood for Mom's On Acid?

[Kolo589]

I dont have a technical answer for that, but I do not believe it's correct.

The parallax adjustment would allow the person who ZEROed the scope to be in a better position though.

Think about it a second.....
Your eye, an object in space (the reticle) aligning to the target.

Look at a small object near you. And the object or spot on a wall across the room behind it.

Shuffle to the left or right. And look at the small object, and whats behind it...

The object, (substitute for a reticle) never moved, but your eye did. And whats lined up behind the object has shifted.

In my case, sitting in the living room.... looking at the little 'fob' on the chain of the ceiling fan, and the spot on the ceiling behind it. Move my head to one side.... the spot on the cieling behind it moves too. Imagine, that fob was the reticle of a rifle scope- bagged in solid position that doesnt move. That shift in eye placement shifts the target you see.

Even setting parallax this will happen. It will significantly reduce the error, but there is still error induced from it.

This is the reason why proper/REPEATABLE cheekweld is critical when using a scope. Its only your eye- which can move- and the reticle a fixed object.... only 2 points of reference drawing a direct line to the target.

With irons, the front and rear sight HAVE to be lined up, which eliminates eye placement/cheekweld as a variable.

So.... because the shape and size/shape of peoples heads/cheek/ cheekbone are different, a scoped rifle MUST be zero'd for 1 shooter. With that variable of eye placement, it wont zero for a lot of other people. Though, they will be VERY CLOSE, it wont be perfect.

Kind of the same with a shotgun with a bead front sight. Only 1 point of reference and your eye- if you shift to one side, you'll be aiming off. Though a shotgun is usually easy to aim because you should be looking straight down the barrel at the bead.

The point of parallax adjustment on a scope is to put the reticle and the target image on the same focal plane (both objects in perfect focus as seen by the shooter). So instead of looking at a 3D view with reticle then target in the background, you have reticle and target in the same plane which creates a 2D image (at the distance of the target).

It would be the same thing as drawing crosshairs on a painting and then moving your eye in relation to that painting. The crosshairs don't move and remain on target.

If you have proper eye relief for the scope, then the image you're seeing for the target and reticle should not change with relation to the position of your eye.


Again, that's my understanding of scope parallax... if that's incorrect, I'm more than happy to receive an education on the subject.

[Pthfndr]

Can you explain in detail how closer or farther to the sight changes elevation?

You are changing the sight radius. The distance from your eye to the front sight is part of that. It may be a small part when you're talking 30"+ from the rear sight to the front sight, but it adds up.

For example, the Warner Vernier rear sight, from their web page:
True 1/4 minute movement at 35.81 inches.
#1 and #2 are 32 TPI.LH. Yielding true angular movement at a radius of 35.810 ".

The serious players in Palma competition check their sights with a dial indicator to verify the amount of movement and will mount them at a specific sight radius so they know exactly how much each adjustment yields.

If you change the sight radius the adjustment no longer gives a true 1/4 moa adjustment. If you were to move your head back or forward without adjusting the sight it will cause a change in POI. Much more noticeable at long range than at, say, 100 yards.

first thought which I posted, was that it was eliminated with 2 reference points instead of 1.

With iron sights you do not have 2 reference points. You have three. Rear sight, front sight, target. And all 3 have to align with your eye. With a scope, once you adjust out any parallax error you have 1 reference point. The reticle. (see kolo589's explanation). Assuming one has adjusted for parallax, windage and elevation correctly (I know, big assumption) you put the reticle on the target, focus your eye on the reticle (which of course one has centered on the target ) and pull the trigger.

[Pthfndr]

kolo589

That's as good an explanation as any, and one that anyone can understand.