Question For The Thinkers

[MePlat]

Lets say one has a handgun with a 12 inch sight radius and at the instance of firing one had a sight misalignment of 3 MOA what would the error be if the sight radius was 6 inches?  Maybe 4 inches?
Would it be the same,  more,   or less?
Or if the sight radius was 6 inches with a sight misalignment of 2 MOA what would it be if the sight radius was 12 inches?

[Graybeard]

MOA is a radian measurement so sight radius would not matter. Had you said a fixed distance say 0.003" of sight misalignment then the on target error would change with sight radius and the longer the sight radius the less the on target error. That is why generally speaking the longer the sight radius the more accurately you can shoot the gun.

[Glanceblamm]

This is a tough question and a good one.

I do know that if you were putting siding on your house, and your line was 1/8" off plumb at the starting point, you could easily be 1-3/4" off plumb at the far end.

If your 12" barrel was off by 3moa when fired the distance that the target would me missed would be massive at the other end but yet unimportant regarding your question.
If the radius was reduced to 6" you would think that the miss would be app half the distance of the 12" radious.

I am sorry to say that I am not one of those thinkers. The overall differences are going to be very sensitive even if you start sawing off the 12" tube at increments that are as small as 1/32nd of an inch.
You would think that this could be calculated though to get some exact numbers.

[Glanceblamm]

What Graybeard Said! (sorry, was a close posting matter)

In my first response, I had assumed that the 12" tube was already aligned, but had been jerked out of the said alignment at the last instant while previously being being focused on a known, which would have been the target in this case.

[MePlat]

Kinda hard fishoing for answers isn't it.  3 MOA is a fixed measuremaent.  .0105 ".  So if the 12 inch sight radius was in error of that amount what would the error be at the 6 inch radius?
I think you guys know what I am getting at.  That is why I entitled the post "Question For The Thinkers".

[Graybeard]

No honestly I don't understand what you're asking.

MOA is a measure of ANGLE NOT DISTANCE. You cannot say that MOA regardless of the number attached to it is a linear measurement until you add in the distance away that MOA applies to.

For instance ONE MOA is a bit over one inch at 100 yards ONLY. At any other distance it is some totally different amount. MOA is not a measure of distance but of angle. A circle contains 360 degrees and each degree contains 60 minutes and each minute contains 60 second. Minute of angle is what MOA means and it is therefore 1/60 of 1/360 of a circle.

If you have an aiming error of some fixed MOA it matters not what the sight radius is that is an angular error not a finite distance error. Changing the sight radius will not change the on target error IF the MOA error remains constant.

I just don't understand what your question is.

[MePlat]

Graybeard ok I will say that the sighting error is 3 minutes of a degree or .0105 inches for the 12 inch sight radius.  Now what would the error be at the 6 inch radius.
It can't be any simpler than that.  What makes it so difficult to answer is that it brings new light what so many want to believe about short sight radius vs long sight radius.
So this question is vexing because it conflicts with what we want to believe and what is a measurable  fact.

[williamlayton]

Thinker ??  Opinionated?? YES!
Now sighting is a straight line question. MOA makes this straight line issue a cone---the tip being the front sights and the angle of deflection (off center aiming) can be any degree.
I agree with GB, the sight radius makes accuracy easier---I guess the best way too see this is if the barrel extended to the target an angle of defection would be less than if 50 feet from the target.
Blessings

[MePlat]

No one can still come up with the answer?   

[unspellable]

This is an example of why you have to ask the right question and get the terms correct.  A MOA is a measure of angle as Greybeard states and is independent of sighting radius.

I think what we are really trying to resolve here is how sight radius relates to aiming error.  If the front sight is off by some given distance, say 0.05 inch, the the error in aiming will be inversely proportional to the sight radius.  A four inch sight radius will result in twice the error at the target that is produced with an eight inch sight radius.

Lets assume 50 yards to the target, a 0.05 inch misalignment.  With a four inch sight radius the point of impact will be shifted approximately 22.5 inches.  With an eight inch sight radius the point of impact will be shifted approximately 11.25 inches.

[MePlat]

If you have a sight misalignment of .0105 on a 12 inch radius what would the misalignment be at the 6 inch radius.  I am not talking about the same misalignment on both and I believe most know that what I am really asking without having to write a long descriptive paragraph.
                               how much
                                  here
      ______________________________________
         
      o                              6 "                             12 "
                                 
                                                              .0105" misalignment

Now does everyone get it?

[sui generis]

An aiming error of 3MOA would result in a sight misalignment of .0105" (approx.) for a 12" sight radius.
The same aiming error would result in a sight misalignment of .00525" (approx.) for a 6" sight radius.

Or,

A sight misalignment of .0105" with a 12" sight radius would produce an aiming error of 3MOA (approx.).
The same misalignment would produce an aiming error of 6MOA (approx.) with a 6" sight radius.

MOA tells nothing about actual group size unless you know the range.

Now, what was the question?

[MePlat]

sui generis  your first answer was correct  the second isn't what I asked for.

If you are capable of holding a 3 MOA error with a 12 inch radius you are capable of holding a 3 MOA with a 6 inch radius.
If you are capable of holding a 3 moa error with a 6 inch radius you are capable of holding the same with a 12 inch

Mathamatical fact. period.  Now what is the real reason we can't shoot short sight radiuses equally as well?
Could it be mental etc. ?

[ncsurveyor]

sui generis  your first answer was correct  the second isn't what I asked for.

If you are capable of holding a 3 MOA error with a 12 inch radius you are capable of holding a 3 MOA with a 6 inch radius.
If you are capable of holding a 3 moa error with a 6 inch radius you are capable of holding the same with a 12 inch

Mathamatical fact. period.  Now what is the real reason we can't shoot short sight radiuses equally as well?
Could it be mental etc. ?

From a purely analytical standpoint, as I had to look up the exact defintion of "sight radius" and I shoot both a Glock sub compact, and a S&W 29N.  To be honest I never analyzed how they shot in comparison to one another, so I never knew there was a problem.

So, given my total blissful ignorance on this situation, let me say that something about your "if your capable statements" is not adding up.  I need to pontificate on this a little.

But my initial impression is that with open sights ultimately you are "eyeballing" the equality of the distance between the front post and the edges of the notch in the rear sight.  If your judgement error is +/- "X", than simple logic suggests that X/6 is greater than X/12 - therefore the angular error is greater in the shorter sight radius.

[Glanceblamm]

sui generis  your first answer was correct  the second isn't what I asked for.

If you are capable of holding a 3 MOA error with a 12 inch radius you are capable of holding a 3 MOA with a 6 inch radius.
If you are capable of holding a 3 moa error with a 6 inch radius you are capable of holding the same with a 12 inch

Mathamatical fact. period.  Now what is the real reason we can't shoot short sight radiuses equally as well?
Could it be mental etc. ?

From a purely analytical standpoint, as I had to look up the exact defintion of "sight radius" and I shoot both a Glock sub compact, and a S&W 29N.  To be honest I never analyzed how they shot in comparison to one another, so I never knew there was a problem.

So, given my total blissful ignorance on this situation, let me say that something about your "if your capable statements" is not adding up.  I need to pontificate on this a little.

But my initial impression is that with open sights ultimately you are "eyeballing" the equality of the distance between the front post and the edges of the notch in the rear sight.  If your judgement error is +/- "X", than simple logic suggests that X/6 is greater than X/12 - therefore the angular error is greater in the shorter sight radius.

This is starting to make some sense as the angular error of the shorter sight radious would be greater than its's longer counter part over the same range and focal point.
I think that this is the very same reason that it is to ones advantage to mount a scope as low as possible on a rifle.
I will shut up now...Good Read

[MePlat]

I am talking capabilities here only.

We all know that a .005 error on a 6 inch radius is more that a .005' error on a 12 inch radius.  But if at the moment of firing a .005 error on a 12 inch would shrink to a 6 inch radius the error would only be .0025'. Conversely the .005 error on a 6 inch would jump to a .010' error on a 12.
This is mathematical fact period.  It can't be discussed
Could we be using sight radius to cover up our own shortcomings in shooting.  Mathematical fact doesn't support our excuse.
I quit using it years ago and have accepted my shortcomings in myself and have quit trying to dredge up excuses. Unless I know the person I am talking to is so shooting challenged that I know they would believe anything.

[ncsurveyor]

I am talking capabilities here only.

We all know that a .005 error on a 6 inch radius is more that a .005' error on a 12 inch radius.  But if at the moment of firing a .005 error on a 12 inch would shrink to a 6 inch radius the error would only be .0025'. Conversely the .005 error on a 6 inch would jump to a .010' error on a 12.
This is mathematical fact period.  It can't be discussed
Could we be using sight radius to cover up our own shortcomings in shooting.  Mathematical fact doesn't support our excuse.
I quit using it years ago and have accepted my shortcomings in myself and have quit trying to dredge up excuses. Unless I know the person I am talking to is so shooting challenged that I know they would believe anything.

Using your logic, if I can then discern that .0025 at 6", than I should be able to discern it at 12", then if I can discern .0025 at 12", why can't I discern .00125 at 6"?  And if I can discern .00125 at 6", I should be able to discern it at 12".  etc etc etc.  Eventually everything will be zero and we should be able to have no detectable error even if the front sight is behind the back sight.

I will grant you that a 0.005 error on a 12" sight radius would equate to .0025 at a 6" but that does not mean I can discern that 0.0025.

The mathematical fact is that the rear sight is a set distance from the shooter,
the human eye can discern space between the blade and the rear sight,
the eyes discern that gap at the fixed distance of the rear sight. 
that discernemnt is subject to a fixed error, at the fixed rear sight,
this error will manifest itself greater (in the target) the closer the blade is to the rear sight.

Maybe your shooting shortcomings are because of your short sight radius?

[MePlat]

ncsurveyor:  You are not going to change mathematical fact.  I know what you are trying to do is conjer up some intangible.  I am not discerning.  I am saying if you happen to have a given error at the moment of firing.  Not what we are able to discern  The error could be caused by other things.
If you me or anyone else has a .005 error at the moment of firing on a 12 inch radius it would be .0025 if the radius suddenly shrunk to 6 inch instead. not more as some would have you to believe.  That is how they use sight radius to cover up their shortcomings.
It just does not happen.
You know that so come clean.

[ncsurveyor]

 

I would like to say I am done with this discussion, but I'm not.  And its 4:00pm, so its time for me to go home.

Hopefully, someone else will straighten this out for you, before I come back to it tomorrow.

But tell me this:  A rear sight notch of 1/8inch.  A front blade of 1/16th inch.  How do you know if you got it centered?

Is it the fact that you have the same gap on both sides, +/- error,

OR is it because you have 0degrees, 2 minutes, and 37" of angle from the front sight, to your eye, back to the rear sight?

I'm not being the devils advocate here, nor do I change mathematical fact.  Math is my bread and butter.  And I love butter.

[MePlat]

First off let me apologize for even posting this question.  I could have made a somewhat better question than the first one.  But I even made a diagram a few post down and people still could answer a simple question except one:   sui generis .
I should have known that something simple would be turned into a complicated quagmire because no one wants go against tradition in explaining shooter shortcomings because it is easier to blame the gun etc. than ourselves.
If you are capable of holding a give moa degree accuracy with a long radius you are capable of holding it with a short sight radius and viseversa.
moa is a numerical value whether anyone likes it or not.

[MePlat]

Oh yes this will be my last post on the subject.  I have learned a lesson for sure.

Graybeard, Moderator (Moderators) do what ever you want with this thread since at this point it has degressed to a post on sight notch width, blade width, the dark or the moon, how one holds their mouth,  etc.. rather than mathematical fact that can't be disputed

Sorry for the post.

[ncsurveyor]

Wow, sir, I certainly did not expect you to take it so hard.

If that is the way you take opposition to your view, by all means, be done with this post.

But I think it would serve all those that viewed this thread to know the mathematical truth.

You have one mathematical fact, that being the geometric proof that .005 subtended at 12" equates to .0025 subtended at 6".  Which also leads to .00042 subtended at 1".  By this logic, 0.0 will be subtended if the sight radius was zero.  So in order to perfect open sight shooting, physically place your front sight on your rear sight.  This is obviously not logical.

You are looking at the whole thing in the length of the barrel, and not the whole system, which, despite the congruency of sides you state, does in fact take into consideration the distance from the shooters eye to the rear sight, and ultimately, how well they can determine the blade to be in the center of that rear sight.



Sorry to disagree with you, but that's life.

[jcn59]

I youse a srewdriver to changze me sites and a cahlipper to missuer  my goups.

Now beat me.

[Chris Potts]

In my mind there are primarily two things that would have an influence on accuracy in your model.

1.  Consistency of sight alignment.  The human eye, as amazing as it is, cannot exactly center the front sight in the rear sight notch.  One time you may be slightly low and left the next time you could be high and right.  The sight will appear to be centered each time but it isn't.  It is merely centered as close as your eye can detect.  This is the reason increased accuracy with a longer barrel.  If your eye can center the front sight in the rear sight to +/- .05", the aiming error with a 6" radius will be twice the aiming error of a 12" sight radius.

2. Steadiness of aim.  I think that this may be what you are thinking about.  There will always be some movement in your point of aim because you can't hold the gun perfectly still.  This would not be influenced greatly by barrel length.  The only reason that it may be influenced is because the extra weight of the longer barrel might help to dampen the movement in your hands

Sight alignment is not going to vary by a certain moa as you have stated.  The front sight is going to be misaligned in the rear sight by a certain decimal amount from center.  I think this may be where we disagree.  If I am not understanding you correctly please clarify.

Chris

[deltecs]

My understanding of the question is if one can hold 3 MOA with a 6" barrel, then one can hold a 3 MOA with a 12" and vice versa.  However, with the longer sight picture, one can hold a substantially closer MOA than one with a short barrel.  Just because someone can hold a 3 MOA with the short barrel does not mean he cannot hold a 1 MOA with a longer one.  Regardless of MOA holds, it is much easier to accurately determine straight line measurements using longer distances than shorter ones.  It is mathematically proved that a small error within a short distance is magnified at longer ones.  Thus any radian error from the straight line sight picture within a given distance is magnified at a longer distance, if the radian error is the same.  Take a transit for example.  If the level is off 1 radian degree and the distance is 10', the terminal vertical error is minimal.  Take the same sight picture to a mountain 10 miles away and the vertical difference off from true level is substantial.  The same principle works laterally or horizontally, as in target acquisition with a radian error in sight picture, either laterally or vertically.

[KN]

deltecs's answer is the best I have seen yet to the question he was trying to ask. Look at it this way, If your sight picture is off .010" at the front sight with a six inch barrel and also with a 12" barrel, the sight angle error changes between the two and you are more accurate with the longer barrel. Even though the blade error is the same for both the angle "MOA" is only half for the longer barrel compared to the shorter barrel. The way you posted the question, GB was right. MOA is MOA no mater how long the barrel is, accuracy stays the same.

[MePlat]

Let me enter this one more time for those. of you trying to turn something easy into something hard
I never said the same error on both sight radiuses period.  I originally said a 3 MOA error in sight alignment on a 12 inch what would it be on a 6 inch?  It would be 3 MOA .  That is the answer.  Nothing more nothing less

12X2=24  24x3.14159=75.39816"  75.39816/21600=.0034906 (1 MOA ) .0034906X3=.0104718" sight misalignment.

If on a 12 inch radius with a sight misalignment of 3 MOA the point at 6 inches will be half of that.

6X2=12  12X3.14159=37.69908  37.69908/21600=.0017453  (1MOA)  .0017453X3=.0052359"  Half

Now the same is true but in reverse going from a short radius to a long.  A given error on a short radius doesn't jump to some unbelievable amount like many believe but is a constant MOA measurement out to infinity.

To prove this 3600 inches in one hundred yards   3600/12=300  300X.0104718= 3.14154  which is 3 MOA
Don't believe it?  3600X2=7200  7200X3.14159=22619.448"/21600=1.0471966 (1MOA)  1.0471966X3=3.1415898"

Due to the limited number of decimals on my calculator there is a very slight deviation from the true MOA at 100 yards and the 3 MOA on a sight radius when mulitiplied  but they are the same.

Now you guys figure the 3 MOA misalignment on a 6 inch radius out to 100 yards and see if there is some black magic causing the ungainly, unproportional jump in misalignment.  

There isn't.  Anyone with calculator with the ability to figure angle, degrees etc. want to have a go at it?
Notice notice notice I did not say .0104718" misalignment on both .  THAT WAS NOT the question so please don't answer a question that wasn't asked.  We can what if forever but that does not change the question.


That is all for me.

[ncsurveyor]

You said earlier that if you can hold 3moa with a 12" sight radius, than you can hold  3moa at a 6" sight radius.

This is not correct.

If you can hold 3moa with a 12" sight radius, than you are in effect holding a 3moa at a point halfway up THAT PARTICULAR SIGHT radius.  It does not follow that you can move the front sight back to the 6" mark and have that same MOA error.

The sight picture (and therefore accuracy) is dependant soley on the (two dimensional) location of blade within the rear sight, regardless of sight radius, and therefore, regardless of the MOA between the line of fire and line of sight. 

However,the error will manifest itself greater in a short sight radius, as opposed to a long one.

I understand your theory, but your starting supposition is incorrect.

[Castaway]

I've read and reread the question and answers and the question restated and am still not sure what is being asked.  Guess I'm not a thinker.  For simplicities sake, the formula for error as it relates to sight radius is:

Radius(Error)/distance to target 

All measures must be in the same unit

[unspellable]

I have a number of answers. I have a high level of confidence in those answers.  But I'm still trying to figure out what the question is.