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LCpl Kutches
10-20-2013, 6:21 PM
I just went to the range. Was talking with the range master and he allowed me to shoot his bolt action 6.8 Grendal Rifle.

After placing five shots at 300 yards within 2" inches. He smiled at me and shook my hand. Said I was a sub moa shooter.

I have no idea what sub moa is or moa.

What is moa? How can I learn this?

Thank you.

decepticon6551
10-20-2013, 6:24 PM
MOA - Minute of angle
http://nssf.org/video/facts/MOA.cfm

More gun & cgn acronyms here
http://www.calguns.net/calgunforum/showthread.php?t=78606

ExtremeX
10-20-2013, 6:57 PM
This is also worth a read...

http://www.caprc.com/forums/viewtopic.php?f=28&t=222

David13
10-20-2013, 7:02 PM
Motorcycle Owners of America.
Oh, sorry, wrong forum.
dc

VictorFranko
10-20-2013, 7:12 PM
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?

Scuba951
10-20-2013, 7:15 PM
Simple answer: MOA = minute of angle.
1 MOA is equal to 1" at 100 yards.

DeCloaK
10-20-2013, 7:16 PM
Since we are nitpicking. I'm sure it was a 6.5 Grendel...because a 6.8 is not that accurate. :p

2013 TT Concrete Gorilla

760knox
10-20-2013, 7:16 PM
NOOOOOO, MOA=Moment Of Action!

xrMike
10-20-2013, 7:19 PM
Take a circle and cut it into 360 equal slices.

Take ONE of those slices and cut it into 60 more equal slices.

One of those slices = 1 MOA.

Oh, and good shooting!

CrippledPidgeon
10-20-2013, 7:28 PM
Take a circle and cut it into 360 equal slices.

Take ONE of those slices and cut it into 60 more equal slices.

One of those slices = 1 MOA.

Oh, and good shooting!

For a bit of clarity:

Take a circle, and cut it into 360 equal slices. Each slice is 1 degree.
Take one of those slices and cut it into 60 more equal slices. One of those slices is 1 minute of angle.

When it comes to shooting, 1 minute of angle is about equal to an inch at 100 yards. A group smaller than 1 inch in diameter at 100 yards is called sub-moa, or is less than 1 MOA in diameter.

Etymological trivia: "sub" is a latin preposition meaning "under." So submarine is a vessel that goes under the water. Subterranian literally means underground. Subsonic is an object travelling slower than the speed of sound. Submachine gun is a machine gun that is smaller and shoots less powerful cartridges than a regular machine gun. And sub-moa is less than a minute of angle.

ExtremeX
10-20-2013, 7:35 PM
Simple answer: MOA = minute of angle.
1 MOA is equal to 1" at 100 yards.

Just to be accurate 1 MOA = 1.047" @ 100 yards.

Most people just round to 1" for the sake of simplicity.

At extended ranges the full value holds more importance.

Manolito
10-20-2013, 7:49 PM
Azimuth and Azimuth Micrometer Scales.

(1) The azimuth scale (Figure 4-3) is located below the magnetic compass housing. It is graduated in 100-mil increments from 0 to 6,400 mils and is numbered every 200 mils. The portion of the azimuth scale from 3,200 mils through 6,400 mils has a second 0-3200 scale numbered in red from the black 32 through the large black 0 on the azimuth scale.

Could be tthe corporal is in artillery but then again every Marine is a rifleman?

JMP
10-20-2013, 8:01 PM
100 yards Tan(pi/180/60) x 3600" = 1.047"
200 yards Tan(pi/180/60) x 7200" = 2.094"
300 yards Tan(pi/180/60) x 10800" = 3.142"
400 yards Tan(pi/180/60) x 14400" = 4.189"
500 yards Tan(pi/180/60) x 18000" = 5.236"
600 yards Tan(pi/180/60) x 21600" = 6.283"
700 yards Tan(pi/180/60) x 25200" = 7.33"
800 yards Tan(pi/180/60) x 28800" = 8.378"
900 yards Tan(pi/180/60) x 32400" = 9.425"
1000 yards Tan(pi/180/60) x 36000" = 10.472"
1100 yards Tan(pi/180/60) x 39600" = 11.519"
1200 yards Tan(pi/180/60) x 43200" = 12.566"
1300 yards Tan(pi/180/60) x 46800" = 13.614"
1400 yards Tan(pi/180/60) x 50400" = 14.661"
1500 yards Tan(pi/180/60) x 54000" = 15.708"
1600 yards Tan(pi/180/60) x 57600" = 16.755"
1700 yards Tan(pi/180/60) x 61200" = 17.802"
1800 yards Tan(pi/180/60) x 64800" = 18.85"
1900 yards Tan(pi/180/60) x 68400" = 19.897"
2000 yards Tan(pi/180/60) x 72000" = 20.944"
2100 yards Tan(pi/180/60) x 75600" = 21.991"
2200 yards Tan(pi/180/60) x 79200" = 23.038"
2300 yards Tan(pi/180/60) x 82800" = 24.086"
2400 yards Tan(pi/180/60) x 86400" = 25.133"
2500 yards Tan(pi/180/60) x 90000" = 26.18"
2600 yards Tan(pi/180/60) x 93600" = 27.227"
2700 yards Tan(pi/180/60) x 97200" = 28.274"
2800 yards Tan(pi/180/60) x 100800" = 29.322"
2900 yards Tan(pi/180/60) x 104400" = 30.369"
3000 yards Tan(pi/180/60) x 108000" = 31.416"

SonofWWIIDI
10-20-2013, 8:14 PM
"Mother of anchovies!"

"Mall of America"

"Museum of art"

:D

64physhy
10-20-2013, 8:25 PM
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?

It's not. I'm sure Snipers learn about it in Sniper school, but it isn't covered in boot camp. We just learn sight alignment, sight picture, safety, trigger control, breathing, etc and how to make windage/elevation adjustments to get the rounds center mass. I don't remember learning anything about MOA when I was a recruit 23 years ago, and I know it wasn't taught when I was a D.I.

Garandimal
10-20-2013, 8:35 PM
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?

The 'new' Corps... :D

(Snipers use 'mils')


...We just learn sight alignment...

W/o MOA? How do you explain wind correction or 'clicks'?




GR

6mmintl
10-20-2013, 8:39 PM
64physhy 64physhy Senior Member and LCpl Kutches LCpl Kutches

We (both of you and I ) are riflemen, non U. S M. C. people lack basic skills in shooting accurately no matter what the distance.

http://pic20.picturetrail.com/VOL149/8996569/19640107/394844974.jpg

JMP
10-20-2013, 9:16 PM
It's not. I'm sure Snipers learn about it in Sniper school, but it isn't covered in boot camp.

I thought the military used MRADs. Here's the MRAD measurements:

100 yards Tan(1/1000) x 3600" = 3.600"
200 yards Tan(1/1000) x 7200" = 7.200"
300 yards Tan(1/1000) x 10800" = 10.800"
400 yards Tan(1/1000) x 14400" = 14.400"
500 yards Tan(1/1000) x 18000" = 18.000"
600 yards Tan(1/1000) x 21600" = 21.600"
700 yards Tan(1/1000) x 25200" = 25.200"
800 yards Tan(1/1000) x 28800" = 28.800"
900 yards Tan(1/1000) x 32400" = 32.400"
1000 yards Tan(1/1000) x 36000" = 36.000"
1100 yards Tan(1/1000) x 39600" = 39.600"
1200 yards Tan(1/1000) x 43200" = 43.200"
1300 yards Tan(1/1000) x 46800" = 46.800"
1400 yards Tan(1/1000) x 50400" = 50.400"
1500 yards Tan(1/1000) x 54000" = 54.000"
1600 yards Tan(1/1000) x 57600" = 57.600"
1700 yards Tan(1/1000) x 61200" = 61.200"
1800 yards Tan(1/1000) x 64800" = 64.800"
1900 yards Tan(1/1000) x 68400" = 68.400"
2000 yards Tan(1/1000) x 72000" = 72.000"
2100 yards Tan(1/1000) x 75600" = 75.600"
2200 yards Tan(1/1000) x 79200" = 79.200"
2300 yards Tan(1/1000) x 82800" = 82.800"
2400 yards Tan(1/1000) x 86400" = 86.400"
2500 yards Tan(1/1000) x 90000" = 90.000"
2600 yards Tan(1/1000) x 93600" = 93.600"
2700 yards Tan(1/1000) x 97200" = 97.200"
2800 yards Tan(1/1000) x 100800" = 100.800"
2900 yards Tan(1/1000) x 104400" = 104.400"
3000 yards Tan(1/1000) x 108000" = 108.000"

Phaedrus2129
10-20-2013, 9:33 PM
A moa is an extinct flightless bird from New Zealand.

gwgn02
10-20-2013, 11:03 PM
hey Moa! knyuk knyuk

kalimus
10-21-2013, 6:20 AM
Minute of Arc

someoneeasy
10-21-2013, 8:56 AM
It's not. I'm sure Snipers learn about it in Sniper school, but it isn't covered in boot camp. We just learn sight alignment, sight picture, safety, trigger control, breathing, etc and how to make windage/elevation adjustments to get the rounds center mass. I don't remember learning anything about MOA when I was a recruit 23 years ago, and I know it wasn't taught when I was a D.I.

It wasn't covered when I was in either. We never used any form of optics, just iron sights. It was clicks to adjust for our elevation and windage. First time I ever heard of MOA was after being on calguns, haha

I'm not sure what they have recruits qualify with now, but I know you qualify with what you're issued so I think they started having Marines qualify with the ACOG.

I remember when qualifying, I was shooting next to a recon Marine who was issued the M4 so he had to qualify with the M4. He was good out to 300 yards, but was having issues at 500 yards.

chomomo
10-21-2013, 12:33 PM
[QUOTE=someoneeasy;12588032]It wasn't covered when I was in either. We never used any form of optics, just iron sights. It was clicks to adjust for our elevation and windage. First time I ever heard of MOA was after being on calguns,


Pretty much this devil dick. Windage, elevation, trigger control, and breathing were the key points emphasized back in the 90's when I went through MCRD in San Diego. The range coaches would hit up the same key points for yearly 2 week qualification. Also remember when you fire some else's, that weapon and scope is zeroed into to that individual.

rm1911
10-21-2013, 3:40 PM
[QUOTE=someoneeasy;12588032]It wasn't covered when I was in either. We never used any form of optics, just iron sights. It was clicks to adjust for our elevation and windage. First time I ever heard of MOA was after being on calguns,


Pretty much this devil dick. Windage, elevation, trigger control, and breathing were the key points emphasized back in the 90's when I went through MCRD in San Diego. The range coaches would hit up the same key points for yearly 2 week qualification. Also remember when you fire some else's, that weapon and scope is zeroed into to that individual.

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.

chomomo
10-21-2013, 7:00 PM
The reason being is that everyone is unique. Eyesight, stance, shooting positions(s), training, body size, weight, and height. This is crucial when viewing down iron sights and or a scope.

daveinwoodland
10-21-2013, 7:09 PM
I was told MOA is an acronym for GOD.

Mother Of All

LCpl Kutches
10-21-2013, 7:47 PM
In the Marine Corps I learned clicks. Adjusting clicks up or down and right or left.

My shots were measured by what I could hit black with iron sites at 100 yrds, 300 yards, 500 yards and then the walk in at 100 yrds. Muscle usage, dry firing, parade sling adjustment, sitting, standing, prone, bone structure usage, unsupported shooting and supported shooting.

Keeping my distance shots relaxed, and always saying "breath in, breath out, slow steady squeeze, slow and Release.

Terms like Moa I have never heard of before, I at least don't remember it.

But its a good idea to learn new things and understand better how to understand how to shoot.

RuggedJay
10-21-2013, 9:05 PM
In the Marine Corps I learned clicks. Adjusting clicks up or down and right or left.

My shots were measured by what I could hit black with iron sites at 100 yrds, 300 yards, 500 yards and then the walk in at 100 yrds. Muscle usage, dry firing, parade sling adjustment, sitting, standing, prone, bone structure usage, unsupported shooting and supported shooting.

Keeping my distance shots relaxed, and always saying "breath in, breath out, slow steady squeeze, slow and Release.

Terms like Moa I have never heard of before, I at least don't remember it.

But its a good idea to learn new things and understand better how to understand how to shoot.

This is the key part here. MOAs and MILS are ways to understand how well a rifle or a person shoots. But the actual act of shooting has less to do with understanding MOA or MILS than it does with knowing how to carry out fundamentals of sight picture, breath control, trigger control, etc. As evidenced by the OPs story you can be an excellent shooter without knowledge of MILS or MOA.

Knowing MILS or MOA comes more into play if you are adjusting the elevation/windage adjustments on your scope to compensate for bullet drop and wind at further distances.

MOAs and Milliradians are simply different measurement scales of how precisely our shots are grouping.

The MOA is based on the 360 degrees of a circle subdivided into its smallest part. Each degree of the circle is further divided into 60 minutes of angle which roughly corresponds to an inch at 100yards. 1 MOA is 1.035"

Milliradians or "mils" is based on taking a complete circle then subdividing it into 1000 equally sized pie pieces. 1 Mil is about 3.5 MOAs or 3.5"

ducky_0811
10-21-2013, 9:06 PM
In the Marine Corps I learned clicks. Adjusting clicks up or down and right or left.

My shots were measured by what I could hit black with iron sites at 100 yrds, 300 yards, 500 yards and then the walk in at 100 yrds. Muscle usage, dry firing, parade sling adjustment, sitting, standing, prone, bone structure usage, unsupported shooting and supported shooting.

Keeping my distance shots relaxed, and always saying "breath in, breath out, slow steady squeeze, slow and Release.

Terms like Moa I have never heard of before, I at least don't remember it.

But its a good idea to learn new things and understand better how to understand how to shoot.

normally I would let it fly...but I cant, I'm SURE you mean 200/300/500, bc the only 100 yd firing done during quals in the movers at 100 during table 2 fires. you also didnt learn the same "click" adjustments the others are talking about, you are referring to the RCO, unless you are a reservists (which I suspect bc you're located in SF) and dont have RCO's on your rifles. in which case you only shoot the table 1 qual KD course every other year. regardless of that, sounds like you remembered what your PMI taught you just fine, keep em in the black!

oh, and dont worry about trying to shoot MOA with ANY standard service rifle (m16A4,M4A1), esp with issued m855 ammo, these rifles are only required to hold 4" at 100 from the factory. thats why our Able targets are 12", you only need to be a 3MOA shooter to hit black

LCpl Kutches
10-21-2013, 9:53 PM
I wasn't reserve. I have 62% lung capacity and was involuntarily separated from active duty service, Honorably Medically.

I learned on iron sites, but went through SOI/MCT with Rco's.

Forgive my memory, I had a cerebral brain hemmorage and have a bit of trouble being exact on specifics anymore.

Just left 29 palms a few months back.

Thank you all for helping to explain this better. It makes more sense.
MOA, just meant to shoot smaller groupings.

ar15barrels
10-21-2013, 10:04 PM
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
10-21-2013, 10:15 PM
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
10-21-2013, 10:16 PM
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
10-21-2013, 10:20 PM
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
10-22-2013, 12:59 PM
(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
10-22-2013, 5:37 PM
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
10-22-2013, 7:08 PM
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
10-22-2013, 7:24 PM
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
10-22-2013, 8:21 PM
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
10-22-2013, 9:08 PM
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
10-22-2013, 9:43 PM
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
10-22-2013, 9:56 PM
I thought it stood for Mom's On Acid?

Kolo589
10-22-2013, 10:20 PM
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
10-22-2013, 11:39 PM
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
10-22-2013, 11:41 PM
kolo589

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

ar15barrels
10-23-2013, 12:18 AM
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.

Proper adjustment of parallax removes ALL parallax error.
The markings on the knob are rarely correct.
Set parallax by bobbing your eye around behind the fixed gun/scope and groups will improve, significantly.
A misunderstanding of parallax is probably one of the biggest factors keeping most shooters from shooting better groups.

ar15barrels
10-23-2013, 12:21 AM
what you say about vertical stringing doesnt make sense to me.... I dont get how closer or farther to the sight would change elevation.

It changes HOW the gun moves during the time that the bullet is moving down the barrel.
A zeroed rifle takes into account the amount of movement during the bullets travel down the barrel.
That is why zeroing a rifle is a personal thing.
A rifle moves differently in recoil when I am behind it than when you are behind it.

This is also why you zero the rifle in the method you intend to shoot it most.
I zero my longrange guns in prone with a bipod and rear bag.
I zero my hunting guns sitting up and shooting over a pack.

koxx.dta
10-23-2013, 5:21 PM
i understand moa as in 1" for 100 yards but what does this mean with a red dot that says 3 or 4 moa? 4moa red dot would cover 4" of the target at 100 yards?

Pthfndr
10-23-2013, 7:20 PM
i understand moa as in 1" for 100 yards but what does this mean with a red dot that says 3 or 4 moa? 4moa red dot would cover 4" of the target at 100 yards?

Yes.

postal
10-24-2013, 2:02 PM
Interesting.... Thanks Rob, Randall for straightening me out.

1 thing though.....

As to marked parallax settings on a scope, and not being correct... I just found out through personal experience, if you change the fast focus eyepiece, it throws off the marked distance.

I setup a new scope against a blank white wall and adjusted the focus to get the crosshair nice and crisp.... The parallax was WAY OFF.....

Looking at a target at 100y, and setting the knob at 100, adjusting the focus until it's parallax free, is where I left the focus. I figure the ease of quickly dialing distance for parallax was more important than a crisp reticle.

Of course I could go to adjusting the eyepiece and marking the parallax knob for correct distances. Which I'll do during the down season.

CK_32
10-24-2013, 2:32 PM
MOA is Minute of Angle = 1" @ 100 yards.

2" @ 200 yards. Ect.

A common misconception is the measure out side to out side of the holes and call it a day which isn't true. You measure from middle to middle of the holes or out side to out side and divide by the caliber of bullet .308, .223 ect. That is how you read MOA or groups.

Being 2 pages long I'm sure that's been answered and there is a huge pissing contest or it's just veered off topic. Either way that is what it is. Hope it helps.

Pthfndr
10-24-2013, 3:00 PM
You measure from middle to middle of the holes or out side to out side and divide by the caliber of bullet .308, .223 ect. That is how you read MOA or groups.

No, you subtract the bullet caliber diameter.

JMP
10-24-2013, 4:03 PM
Milliradians or "mils" is based on taking a complete circle then subdividing it into 1000 equally sized pie pieces. 1 Mil is about 3.5 MOAs or 3.5"

:confused:

Radian are measured as the ratio of arc length to radius.

The circumference of a circle is 2 * pi * radius

Thus, the number of radians in a complete circle = (2 * pi * radius)/(radius) = 2 * pi.

An MRAD is 1/1000 of a radian.

So, there are actually 2 * pi * 1000 ~ 6283 MRADs in a complete circle.

100 yards = 3600 inches, so the distance is Tan(1/1000) * 3600 = 3.6"

It works much better in the metric since it is a base 10 system.

So, Tan(1/1000)*100 meters = 0.1 meters, or 10 cm @ 100 meters, so each 0.1 MRAD click = 1.0 cm @ 100 meters.

xrMike
10-24-2013, 8:33 PM
Being 2 pages long I'm sure that's been answered and there is a huge pissing contest or it's just veered off topic.Amazingly, no. A rarity on Calguns these days.

postal
10-24-2013, 8:40 PM
Amazingly, no. A rarity on Calguns these days.

...Oh.... dont get me started!!!! :p:p:p:p

Kidding! just kidding!!!! Funny as heck though!

ar15barrels
10-24-2013, 10:22 PM
No, you subtract the bullet caliber diameter.

Its actually more accurate to subtract the diameter of a single lone hole on the exact target as the target paper stretches open as the bullet goes through it.
You will often find that a single bullet hole measures 0.025" smaller on the target paper than the bullet that made the hole.
Say you measure a group as 1.000" outside-outside and you subtract 0.308" bullet diameter.
That leaves you a group size of 0.692"
Then you measure a single bullet hole and it measures 0.280".
Since you are measuring the group with the same measuring method, both values will have similar accuracy/inaccuracy of measurement.
The 0.280" measured hole subtracted from the 1.000" measured group gives a more accurate group size of 0.720"...

Pthfndr
10-24-2013, 10:34 PM
Its actually more accurate to subtract the diameter of a single lone hole on the exact target as the target paper stretches open as the bullet goes through it.
You will often find that a single bullet hole measures 0.025" smaller on the target paper than the bullet that made the hole.
Say you measure a group as 1.000" outside-outside and you subtract 0.308" bullet diameter.
That leaves you a group size of 0.692"
Then you measure a single bullet hole and it measures 0.280".
Since you are measuring the group with the same measuring method, both values will have similar accuracy/inaccuracy of measurement.
The 0.280" measured hole subtracted from the 1.000" measured group gives a more accurate group size of 0.720"...

Yeah, but then group size isn't as small. What fun is that when one is posting a cherry picked picture ;)

My groups are never small enough that 25 thousandths of an inch is going make an impressive difference anyway :)

sjb269
10-27-2013, 4:06 PM
Dammit! Google must be broken again!