MOA Question


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jon8777
April 11, 2010, 11:16 PM
Shot the 223 tonight at 100, 150 and 200 to verify the balistics on my mil-dot chart. I shot 3 shot groups 10 minutes apart with a 3-5 mph wind at my back.

I came home and started looking at the numbers and I need a second opinion to verify my math.

Heres my results for the groups shot from bipods with a rear bag prone on the ground.

100 yards 0.552"
150 yards 0.617"
200 yards 0.733"

In theory I should have shot a 1.104" group at 200 yards, but its grouping smaller as I shoot further. (Typically this gun shoots in the .7-.8" at 200 yards.)

What is the proper way to determine the MOA of this load? Use the 100 yard group as MOA or divide the group size into the yardage and average the 3 distances?

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Zak Smith
April 11, 2010, 11:38 PM
If the sight picture was different, or your shooting position was different at the different ranges, that can account for different levels of accuracy.

If you are consistently shooting 0.7-0.8" at 200 yards, it might be worthwhile to figure out why your leaving accuracy on the table at 100.

jon8777
April 12, 2010, 09:37 PM
I shot the same position and hold.


The scopes a 3200 10x fixed MD

hadmanysons
April 12, 2010, 10:14 PM
Bullets do not fly in a "straight" line all the way down the range. People tend to think of it as a funnel, the further out you get but that is not always true. I wish i had the link to the video explaining it because its hard to describe. Assuming that you an excellent marksmen and everything is staying super consistant between the different ranges, there may be nothing wrong with the group size. The bullets just might be corkscrewing as they get further down range.

Now, this is a new concept to me and i'm not sure i believe it yet either but it is something i have heard of and seen. I might be talking out of my @$$ but this could be what's going on.

Does anyone else remember what i'm talking about?

bhk
April 13, 2010, 01:51 PM
I am not too sure you are using the term MOA accurately, making answering your question a little difficult. MOA stands for 'minute of angle,' and is about 1.05" at one-hundred yards. That would be 2.10 at two hundred, 3.15 at three hundred, etc. Most folks just round this off to 1, 2, and 3 inches.

I think you are really talking about group size. A MOA group at 100 yards (one inch group) has always been an accuracy goal for shooters. Your rifle is shooting considerably under MOA at the ranges you are listing. That is one wonderfully accurate rifle. As far as the groups tighting (in respect to moa) at longer ranges, this is not unheard off and relates to the fact that some bullets take considerable flight time to properly stabilize.

wishin
April 13, 2010, 02:25 PM
I would express your accuracy as follows:

100yds - .55" MOA

150yds - .93" MOA

200yds - 1.47" MOA

All are sub-MOA. To average them out would be mixing apples and oranges IMO. I could be wrong, but that's how I would tell someone what MOA that particular gun shoots.

Zak Smith
April 13, 2010, 02:43 PM
I would express your accuracy as follows:

100yds - .55" MOA

150yds - .93" MOA

200yds - 1.47" MOA

All are sub-MOA. To average them out would be mixing apples and oranges IMO. I could be wrong, but that's how I would tell someone what MOA that particular gun shoots.
__________________
This is all wrong, and using units of " MOA (literally inches MOA) also doesn't make any sense.

0.552" at 100 yards is 0.552/1.0472 = 0.527 MOA
0.617" at 150 yards is 0.617/(1.0472*1.5) = 0.393 MOA
0.733" at 200 yards is 0.773/(1.0472*2) = 0.369 MOA

bhk
April 13, 2010, 02:43 PM
WRONG!!

He is shooting:

.53 MOA at 100 yards (MOA at 100 is 1.05 in.)

.39 MOA at 150 yards (MOA at 150 is 1.58 in.)

.35 MOA at 200 yards (MOA at 200 is 2.10 in.)

Edited: OPPS! ZAC BEAT ME TO THE CORRECTION. Actually Zac's answer is more correct than mine because he is rounding off MOA to four places and I rounded off to two places.

.

jnyork
April 13, 2010, 03:40 PM
If I had a rifle that shot like that I dont think I would be worried about such minor things as this. :)

NMGonzo
April 13, 2010, 04:14 PM
if I can hit a card from a deck taped to the target at a 100 yards I am as happy as I can be.

3:00hold
April 13, 2010, 05:32 PM
Shoot 20 3 shot groups at each range and tell me the average. If 200 yards isn't 2x 100 yards (or greater) then you are going something different or you have a psycological issue with shooting at 100 yards.

Comparing two three shot groups is statistically meaningless.

Loosely, MOA is 1" at 100 yards, 2" at 200 yards, etc.

jon8777
April 13, 2010, 10:01 PM
This is all wrong, and using units of " MOA (literally inches MOA) also doesn't make any sense.

0.552" at 100 yards is 0.552/1.0472 = 0.527 MOA
0.617" at 150 yards is 0.617/(1.0472*1.5) = 0.393 MOA
0.733" at 200 yards is 0.773/(1.0472*2) = 0.369 MOA

As soon as I posted I realized my use of 'MOA' was incorrect.

I am not complaining about the accuracy of the gun. I am very happy with it after last summers looooonnnnggg load testing, gun tuning and final scope selection. Now I need to start verifying my MD guestimates to actuall ground hog 'target' results. I have two ( 2/2 ) field target results with the MD scope so far this year. I am still getting use to using the MD for hold points, its nice but its taking time to get use to.

I was looking for why or what is causing my groups to measure a smaller MOA calculated group sizing as the target is further out.

I am not seeing any signs of keyholes/oblong holes in the target up to 200 yards (rifle ranges max distance) and I have fired 200+ rounds thru this gun working on the load.

When you talk about the funneling of the bullet, my guess is the group will eventually reach a point where the group begins to grow in respect to MOA?

jmr40
April 13, 2010, 10:19 PM
There have been several discussions about this here and at other forums recently. No one has come up with concrete proof to either prove or disprove the theory but a lot of people believe that under the right conditions bullets become more stable after a short distance after being fired. This results in better accuracy than expected at longer ranges. Others theorize that shooters just concentrate better because the target appears smaller at longer ranges.

I've experienced the same thing many times. I believe there is something to the bullet becoming more stable after a point in it's flight, but cannot offer any real proof.

I will only say that with some of my rifles I quite often get groups similar to yours. Some of my rifles shoot the same MOA pretty consistently at all ranges, just as one would expect. Other rifles I own very often shoot as yours did, getting slightly better MOA as the range increases. If I were just concentrating better at the long ranges I would see the same with all of my rifles.

1858
April 13, 2010, 10:27 PM
I was looking for why or what is causing my groups to measure a smaller MOA calculated group sizing as the target is further out.

It may be your sight picture as Zak mentioned. You have a fixed 10X scope so it's quite possible that your brain/eyes/muscles prefer the percieved reduction in reticle movement on the target at 200 yards. That's my best guess since shooting is 90% mental (so they say). If you had a variable scope such as a 3-9x, you could try 3x at 100 yards, 6x at 200 yards and 9x at 300 yards. Now that would be interesting.

:)

Ridgerunner665
April 13, 2010, 10:29 PM
In reference to Zak's first post...

Parallax? Makes sense...the scope is probably preset at 150 or 200 yards.

M1key
April 13, 2010, 10:30 PM
Sub 3/4 inch groups at 200yds with an AR? That's almost competitive in bench rest...

The term is "going to sleep". Seems the boattails rotational pitch slows and stops "wobbling" anywhere around 150 yards. The 200 yard groups are often tighter (MOA-wise) than 100 yard groups. Match shooters have known this for years...

I have noticed it mostly shooting heavier (read longer) 308 match boat-tails from a bolt gun. Groups can run .50 to .75 inches @100 yards and still group .75 inches or less at 200.

1858
April 13, 2010, 10:37 PM
The term is "going to sleep".

I still don't believe this "going to sleep" theory. I'm certainly not saying that it's not true, it's just that I've NEVER worked up a load that was more accurate at 200, 300, 600 or 800 yards compared to 100 yards.

Sub 3/4 inch groups at 200yds with an AR?

Did the OP state that he was shooting an AR? Maybe I missed it.

:)

fractal7
April 13, 2010, 10:45 PM
I just kind of stumbled on this thread and find it pretty interesting. What kind of target are you shooting at? Shape, color etc... If the aiming point gets smaller perhaps its easier to aim at the point rather than the "middle" of say a larger black circle at 100 yards. May not be the answer but just another theory to throw into the mix.

jon8777
April 13, 2010, 10:57 PM
If you had a variable scope such as a 3-9x, you could try 3x at 100 yards, 6x at 200 yards and 9x at 300 yards. Now that would be interesting.

The first scope that was on the rilfe was a 3-9x40 and with variable power settings the groups were the same.

Nope, not an AR... Like to have one but I'd have a mint into one... not that its a bad thing.

So the 'going to sleep' is gun to gun or is it based on the bullet?

M1key
April 13, 2010, 10:57 PM
Sorry, my mind was on "AR" at that moment.

Whatever the phenomenon referred to as "going to sleep" is, it is fact. I have heard this from match shooters using boattails and I have done it myself on a number of occasions...at least to 200 yards.

I understand VLD bullets (very low drag) with protracted boattails were developed (in part) to minimize this effect. Has something to do with ballistic coeffiecient of friction...but I slept through that part of the class.

Lapua 170 match have a bit of a rebated boattail.

jon8777
April 13, 2010, 11:02 PM
I just kind of stumbled on this thread and find it pretty interesting. What kind of target are you shooting at? Shape, color etc... If the aiming point gets smaller perhaps its easier to aim at the point rather than the "middle" of say a larger black circle at 100 yards. May not be the answer but just another theory to throw into the mix.

B/W grid compliments of the Oce plotter from work.

I have tried combinations of black, yellow and red home grown targets over the years and never noticed a difference in groups. Some people see different colors better.

jon8777
April 13, 2010, 11:05 PM
Sorry, my mind was on "AR" at that moment.

Np


Your talking the Barnes VLD bullets?

M1key
April 13, 2010, 11:10 PM
I was thinking Berger...I have a few boxes of their 308 match VLD and they have a very LONG BT and a long OAL...too long for a lot of mag-fed rifles.

jon8777
April 13, 2010, 11:17 PM
Wrong 'B'...

Yes the longer heavier bullets shoot better than the shorter bullets of the same weight.

Length of bullet is not a problem, just not sure if I want to start down the road of working up a new load.

ArthurDent
April 14, 2010, 12:13 AM
3:00hold,

You now have my interest and respect.

I had been reading this thread with some interest and curiosity as I have been working hard to improve my accuracy. The more I study this problem, the harder it gets. This is fun and frustrating!. :)

I had been reading this thread, wondering if there was some new phenomenon of external ballistics I didn't yet know about. I had forgotten the key point of statistics, and you reminded me of it, 3:00hold. Your procedure of averaging groups is exactly correct! :)

I have started a thread, here, on some math I've played with on this subject.

The bottom line results for this particular situation are: For a 3-shot group, you can expect the center-to-center measurement (ctc) to vary over a quite wide range. For instance, if your average ctc measurement for a 3-shot group was 1.0 MOA, you would expect a particular ctc measurement to vary between 0.44 and 1.65, 90% of the time. That is a huge range!

Sooo, jon8777, it is quite easy to believe that your single measurements of 3-shot groups could vary between 0.53 and 0.37 MOA. I would be interested in seeing the results of the averaged measurements as described by 3:00hold.

In any case, I'm still quite jealous. My groups are nowhere near that tight yet.

ArthurDent.

benzy2
April 14, 2010, 01:14 AM
Whatever the phenomenon referred to as "going to sleep" is, it is fact. What exactly makes this fact outside of a few shooters thinking they notice such a phenomenon? I could say since my groups exponentially grow as distance increases that bullets not only travel out in a funnel, they intentionally try to miss what I'm aiming at. Does that make my statement any more fact than yours? Its what happens when I shoot. Must be fact. Right? Its a theory and that's all. Until there is hard data beyond a bunch of guys shooting in the wind it will be nothing more than a theory.

As for what is happening, well, there are a thousand variables to pick from. I would start by removing them one at a time if you really want to get to the bottom of what is happening.

Zak Smith
April 14, 2010, 01:18 AM
We recently had another thread about this that covered it in some detail.

However, I was one of the ones that posted I've never shot a rifle/load that would consistently shoot better at any further distance vs. closer. I have had quite a few loads that shot disproportionately worse at distance, and some that just plain acted funny at all distances.

-z

M1key
April 14, 2010, 01:35 AM
Right. It's just a theory.

Apparently you have never seen it, so you would never be compelled to try and explain it.

I do like cool videos, though. http://www.youtube.com/watch?v=KH9SCbCBHaY

jon8777
April 14, 2010, 06:19 PM
Thats a good video.

I have 5 on record groups with this load at 200 that range from .830 to .733".

I cant not find my 100 yard targets but they range in that .5-.8" range.


If the "going to sleep" groups were hapening to you, would you change something in your load?

1858
April 14, 2010, 06:59 PM
Right. It's just a theory. Apparently you have never seen it, so you would never be compelled to try and explain it. I do like cool videos, though. http://www.youtube.com/watch?v=KH9SCbCBHaY

First off, that video merely shows the output from a computer MODEL, and furthermore, as it stands it's meaningless. Mr. Litz is a talented individual but the video is still meaningless and he should know better. However, if you want to use that video to convince yourself that the "going to sleep" theory is FACT then you're obviously free to do so.

The thing with the "going to sleep" theory is that it's a LAZY rationalization of what might be happening. It's convenient to explain it all away with such a catchy phrase and a neat little video but there are numerous complicated internal and external variables that could account for a reduction in MOA group size as a function of distance.

X MOA could be thought of as a circular area with diameter = X MOA in which the bullets are landing. If you shoot 1 MOA groups at 100 yards, your bullets are landing in an area of 0.861 in^2. However, the area of a 1 MOA circle at 200 yards is 3.45 in^2 and at 300 yards the area is 7.75 in^2. So the area is a function of the square of the group diameter (nothing new here). In other words, if you shoot 1 MOA groups at 300 yards (3 times the distance), your bullets are landing in an area 9 times that of the area enclosed by a 1 MOA circle at 100 yards!

If you wanted to only double the area of the group at 200 yards and triple it at 300 yards compared to the 1 MOA area at 100 yards, you'd need to shoot 1.481" (0.707 MOA) and 1.814" (0.577 MOA) groups at 200 and 300 yards respectively.

The OP mentioned 0.552" groups at 100 yards and 0.733" groups at 200 yards. The area of a 0.552" circle is 0.239 in^2 and the area of a 0.733" circle is 0.422 in^2. So double the distance and almost double the area of the group. Seems reasonable to me ... just as reasonable as the "going to sleep" theory.

Just a thought!

:)

Zak Smith
April 14, 2010, 07:16 PM
The video does not show the path is inconsistent, just that is not exactly straight. IE, if the bullet path per the path graph is the same every time it would not support better accuracy at longer ranges.

JDGray
April 14, 2010, 07:34 PM
I had that Bushnell Elite 3200 10x40 scope, and it had slight parallax at 100yrds, terrible at 200yrds, never did find it parallax free. You've got one fine shooting .223, and if your scope is anything like mine, you must have a very consistant shooting technique to shoot past the parallax error;)

hadmanysons
April 14, 2010, 08:34 PM
Right. It's just a theory.

Apparently you have never seen it, so you would never be compelled to try and explain it.

I do like cool videos, though. http://www.youtube.com/watch?v=KH9SCbCBHaY
That's the video I was talking about! Thanks M1key

benzy2
April 14, 2010, 10:00 PM
Right. It's just a theory.

Apparently you have never seen it, so you would never be compelled to try and explain it.

I do like cool videos, though. http://www.youtube.com/watch?v=KH9SCbCBHaY

That video shows the flight path does not stay in a straight line. It has nothing to do with multiple shots. Their model would show every bullet following the exact same path as well. Its also a youtube video, not quite your scientific standard. Either way it is just a model based on one theory of what is happening, be it true or not. I still don't see 1000 yard matches shooting better MOA than 100 yard matches, at least not in current recollection, but I haven't followed long range competition overly close.

jon8777
April 14, 2010, 10:50 PM
I had that Bushnell Elite 3200 10x40 scope, and it had slight parallax at 100yrds, terrible at 200yrds, never did find it parallax free. You've got one fine shooting .223, and if your scope is anything like mine, you must have a very consistant shooting technique to shoot past the parallax error

For $60 cheaper NIB than they were selling new online, I figured it was worth a gamble and it was 225$ cheaper than the scope I was looking at. I know its far from top shelf, not a Bushnell fan and I figured for a low recoil gun, I'd try it... so far so good.


X MOA could be thought of as a circular area with diameter = X MOA in which the bullets are landing. If you shoot 1 MOA groups at 100 yards, your bullets are landing in an area of 0.861 in^2. However, the area of a 1 MOA circle at 200 yards is 3.45 in^2 and at 300 yards the area is 7.75 in^2. So the area is a function of the square of the group diameter (nothing new here). In other words, if you shoot 1 MOA groups at 300 yards (3 times the distance), your bullets are landing in an area 9 times that of the area enclosed by a 1 MOA circle at 100 yards!

Thats actually a good point... guessing this isnt 1858's first run around the block

DaleA
April 15, 2010, 01:19 AM
It's late, I'm tired but here's a thought somebody else must of thought of before...
line some targets up directly behind each other at 100, 150, 200 etc and fire one group...if the group is 1 inch a 100, 1.5 at 150 and 2 at 200 that's kind of what you'd expect...if the groups at the longer ranges are tighter...well I guess that would lend weight to some of the theories posted here.

scythefwd
April 15, 2010, 01:20 AM
Aim small, miss small. That 200y target looks 1/2 the size of your 100y target? If so, you are holding on a smaller target, and probably being more picky about when you let fly.

oldfool
April 15, 2010, 02:33 AM
I have to throw my vote to "aim small, miss small", also
(which is same as I would interpret the above target ''comparative area" version)
a pretty universal phenomena, tight shooting is a mind game, mental focus, psychology.. not what the eye sees, but what the mind sees

I often shoot tighter when crosshairs literally obscure the target POA, rather than looking for center of a target... either it is fully covered, or it is not, no wandering/wondering about it, no "forgetting" to focus on the crosshairs not on the target, because they are one and same

the statistical argument posed up-thread would be suspect #1, but I think shooter is not referring to the posted one-time sampling, but a far larger sample of repetitive, consistent results over a far far larger sample size

"going to sleep" bullets is intriguing theory, but I see no reason to stretch for such rationalizations given the many subtle variables already in play... variable #1 always being mental

jmr40
April 15, 2010, 06:56 AM
A couple of points I would like to add. I make my own targets. I cut out a template and color in 1/2" squares for my 100 yard targets and 1" squares for my 200 yard targets. To further reduce the chance for aiming error I place the crosshairs only on 1 corner of the square. This eleminates the possibility of the aim small miss small theory. With some of my rifles I shoot consistent MOA at all ranges. With others I consistently see smaller MOA at the longer ranges. The difference is not great.

I'm just a hunter who likes to shoot, not a long range target shooter but with some rifles I will consistently see .75-1" groups at 100 yards and 1"-1.25" groups at 200 yards. I will sometimes get the .5" 100 yard group but it only happens enough to call it lucky.

It has happened to me too many times for me not to believe something is going on other than just "aim small miss small"

3:00hold
April 15, 2010, 08:03 AM
The "bullet going to sleep" theory can be tested very easily. Measure the hole at closer ranges and compare that to the hole at longer ranges - of course you would need to shoot something that allowed for this i.e. left clean holes. The only way that would be possible is if the bullet was vibrating or askew earlier in it's flight path and therefore left a bigger hole.

I'm an engineer, not a physicist, but I can tell you with 100% certianty that there is no way for a certain number of unguided bullets (let's say 10) to diverge from the perfect flight path DIFFERENTLY at closer ranges and then miraculously return to a common point down range. If they all diverge the same way, then the group would still be smaller at closer ranges. The example I described above would be the bullets maintaining the same flight path, just vibrating or turning slightly and leaving a differently shaped hole at closer ranges. Of course, we would be talking about a differnce in the hundredths to thousandths of inches.

There are only 2 ways to get smaller groups at longer ranges. 1) the bullet is guided 2) the hole at closer ranges is bigger.

For what it's worth, I don't think 2 is possible. That would be like a football quarterback throwing a duck at 20 yards that straightens itself at 40 yards.

oldfool
April 15, 2010, 08:15 AM
heckifiknow
but even though OP has apparently shot a lot of groups and seen consistent repeatable patterns, he might (?) be shooting only very few at any one sitting, as in post #1

IF in the habit of always shooting same sequence (100 yards 1st, then 150 yards 2nd, then 200 yards last), AND always starting with a clean barrel, AND shooting so few rounds per session (even though waiting for barrel to go cold between shots), the answer is intuitive enough...

but that's a whole lot of IF stacked up
unlikely the fellow would be doing that

ArthurDent
April 15, 2010, 10:07 AM
I am intrigued! :)

Apparently (post #29), the results are consistent! So much for my guess!

Aim-small, miss-small would be my next guess, BUT...

The possibility of this "going to sleep" thing has me fascinated!

BTW, I've NEVER seen this... just the opposite in fact, but I mostly shoot .22's, and never at longer than 100yds. (That's all my range has.) Usually the .22's will group nicely at 25yds, will spread out some at 50yds, and will be at 2 to 3 times the MOA reading at 100yds. (That's right, 12-times the actual, on-target spread at 100yds!) Only on a couple of really calm days has my MOA at 100yds approached my MOA at 25yds. (Yes, the .22 is a wimpy round.)

(grabbing my popcorn and waiting for more...)

jmr40
April 15, 2010, 03:45 PM
3:00hold.

A football will sometimes start out wobbling and then return to a tighter spiral. Been coaching high school football for 30 years. I've seen it happen more often when the ball is punted than thrown.

A spinning top will often start out wobbly and stabilize into a tight spiral. As they slow down they will start to wobble then correct its self. They will eventually slow to the point where they are no longer stable and fall.

We all know that different bullets stabilize best when the rifling in the barrels is correct for the bullet. Often slower loads produce better accuracy than faster loads. I could see a bullet leaving the muzzle traveling too fast to be stabilized by the rifling and after slowing a bit becoming more stable. This is also why I think the punted football is sometimes less stable at first. It comes off the foot much faster than when thrown and stabilizes after slowing down.

While we cannot see it, and I have no way to prove it, I cannot see why a bullet in flight might not do the same thing.

You are correct in that there is no force that would pull the bullet back to the point of aim. But if all the bullets in a group became stable at the same point in their path, They may well group into a smaller MOA (not actual group size) at longer range than at shorter range. The point of impact may well be farther left, right, up, or down than expected.

I don't offer any of this as proof. This is just a theory I've come up with based on my own observations and reading others comments. I simply don't know, but this makes sense to me.

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