Folks,
The instructor manual say that the front post on a garand and 20" AR is 7moa. It seems about right. I can't seem to make the math work, though.
moa = p/(((R x 2 x 3.1416)/360)/60)
R= distance from eye to front post
p= post width
So, the distance from eye to front post is 22" That is the radius. Times two is the diameter or 44" Times 3.1416 (pi) gives you the circumference or 138.2. Divide by 360 degrees to get .38 inches per degree. Divide again by 60 to get .006 inches per MOA. Standard front post is @ .072. So divide that by .006 and get 12. 12MOA? Where am I going wrong? There should be a way to determine the moa of a front sight on any rifle without actually posting paper at 25yds.
Haven't studied up on it at all, but...
I understand why you measured from the eye, but is it supposed to be from the rear sight?
Not sure what that would do the the calcs.
And it's too late for me to get my brain wrapped around it now.
Greg
Quote from: dart67eb on November 24, 2011, 02:36:47 AM
Folks,
The instructor manual say that the front post on a garand and 20" AR is 7moa. It seems about right. I can't seem to make the math work, though.
moa = p/(((R x 2 x 3.1416)/360)/60)
R= distance from eye to front post
p= post width
So, the distance from eye to front post is 22" That is the radius. Times two is the diameter or 44" Times 3.1416 (pi) gives you the circumference or 138.2. Divide by 360 degrees to get .38 inches per degree. Divide again by 60 to get .006 inches per MOA. Standard front post is @ .072. So divide that by .006 and get 12. 12MOA? Where am I going wrong? There should be a way to determine the moa of a front sight on any rifle without actually posting paper at 25yds.
Your math is correct. I find it easier to do it with trigonometry.
tan θ = width/length, where θ (theta) is your angle in degrees
My Garand front sight is .069", my eye is 30" from the front post.
arctan (.069/30) = .1318° or 7.9 MOA
So, using your example of 22" and .072:
arctan (.072/22) = .1875° or 11.25 MOA
Using your numbers and the way you're calculating it (and not rounding), it also calculates to 11.25.
I wish I knew I could apply trig to shooting when I first learned it. Would've made it a hell of a lot more interesting.
ETA - I have a national match front post on one of my AR's - .048" wide. That would be 7.5 MOA wide at 22 inches.
ETA II: Most online calculators do trig in radians, not degrees. So if you use Google, add "in minutes" to the equation. For those unaware of Google's talents, cut and paste this into the Google toolbar and see the magic: arctan (.069/30) in minutes
Quote from: intheburbs on November 24, 2011, 03:33:50 AM
Quote from: dart67eb on November 24, 2011, 02:36:47 AM
Folks,
The instructor manual say that the front post on a garand and 20" AR is 7moa. It seems about right. I can't seem to make the math work, though.
moa = p/(((R x 2 x 3.1416)/360)/60)
R= distance from eye to front post
p= post width
So, the distance from eye to front post is 22" That is the radius. Times two is the diameter or 44" Times 3.1416 (pi) gives you the circumference or 138.2. Divide by 360 degrees to get .38 inches per degree. Divide again by 60 to get .006 inches per MOA. Standard front post is @ .072. So divide that by .006 and get 12. 12MOA? Where am I going wrong? There should be a way to determine the moa of a front sight on any rifle without actually posting paper at 25yds.
Your math is correct. I find it easier to do it with trigonometry.
tan θ = width/length, where θ (theta) is your angle in degrees
My Garand front sight is .069", my eye is 30" from the front post.
arctan (.069/30) = .1318° or 7.9 MOA
So, using your example of 22" and .072:
arctan (.072/22) = .1875° or 11.25 MOA
Using your numbers and the way you're calculating it (and not rounding), it also calculates to 11.25.
I wish I knew I could apply trig to shooting when I first learned it. Would've made it a hell of a lot more interesting.
ETA - I have a national match front post on one of my AR's - .048" wide. That would be 7.5 MOA wide at 22 inches.
ETA II: Most online calculators do trig in radians, not degrees. So if you use Google, add "in minutes" to the equation. For those unaware of Google's talents, cut and paste this into the Google toolbar and see the magic: arctan (.069/30) in minutes
Thanks. I'm glad somebody remembers trig. Anyway, I'm getting out the tape measure and caliper tomorrow to get the real numbers. We may need to get Dond in on this if we are putting out bad dope.
"For those unaware of Google's talents, cut and paste this into the Google toolbar and see the magic: arctan (.069/30) in minutes"
Now THAT is cool!
Quote from: dart67eb on November 24, 2011, 03:59:16 AMThanks. I'm glad somebody remembers trig. Anyway, I'm getting out the tape measure and caliper tomorrow to get the real numbers. We may need to get Dond in on this if we are putting out bad dope.
Agreed. I always preface any of this info with "figure it out for your own rifle, every rifle is different, etc." I knew my Garand was 8 MOA, so that is the example I usually use.
Quote from: dart67eb on November 24, 2011, 04:09:47 AM
"For those unaware of Google's talents, cut and paste this into the Google toolbar and see the magic: arctan (.069/30) in minutes"
Now THAT is cool!
Yup, all you need is your smartphone, and you can do the calcs right on the line!
There is also the difference in focal plane to consider.
Because the shooter cannot keep both the front post and the target in focus, a nominal front post width of 7.9 MOA to produce an visually apparent 7 MOA sounds about right.
For the purposes of 4 MOA shooting, I find it easiest to put up a 4MOA target at 25 meters and look at it. I can get pretty close, say + or - ~1.5 MOA in the measurement. That is gonna be good enough for range finding out to 500 yards.
Now the trig trick may be best for an oddity rifle like a short barreled rifle. I am not sure what effective size it's front post is other than to say that SPQR complained that it was "like 32 MOA or something!" when he declared his distaste for it. ;D
Techres
P.S. That Google trick is cool! Now I need to take a trig class to have a chance to use it. My engineer father is still mad I evaded trig in school...
I got through trig by drawing out scale diagrams and measureing what I was trying to find! #) Like others, I slap a 1/4 MOA target out there and see how much my front post covers. Many "stock" front posts cover about 8 MOA but this is going to vary with the shooters geometry and sight radius. The Tech Sights on my 10-22 are exactly 4 MOA and I much prefer them over 8. Got a 16" AR and the sight radius is very short. I put a NM front post on it and it's still about 6 MOA, still too big for my likeing. I'll either buy something smaller or chuck it up in a drill press, break out the file and make my own.....O.L.
I used your method, tech. On the SBR the post appeared to be a little over 8 times the width of a 4moa square. Paa! Phooey. Silly communist rifles.
Quote from: floydf on November 24, 2011, 10:27:52 AM
There is also the difference in focal plane to consider.
Because the shooter cannot keep both the front post and the target in focus, a nominal front post width of 7.9 MOA to produce an visually apparent 7 MOA sounds about right.
(emphasis mine)
Folks, I urge you not to get wrapped up trying to figure out why your eye doesn't read the width of your front sight the same as a caliper does.
Take a moment to think this through-
The reason you want to know the width of your front sight is so that it can be used as a range finder, and to assist in hold-offs for windage.
For both of these, you are comparing the visual appearance of a target to the visual appearance of your front sight.
In other words, it is more important to know what size your front sight appears to be, to your eye, than it is to know what the front measures, according to the math.
FWIW, these are the numbers I got:
CMP M1 Garand - 8.85MOA (.085/33)
20" AR - 9.76MOA (.071/25)
Mosin-Nagant 91/30 - 7.19MOA (.081/38.75)
Next, I will line them up on a known sized object at 25yds.
Hey, what's wrong with you people? :-\ Is this all you've got to do on Thanksgiving day? #) ;D ;D
At first glance, what you all have done seems OK, but I'm not about to worry about it tonight. I'll check it out tomorrow, perhaps with a little different approach. It also seems that I've read somewhere that the front sights on some ARs are different.
OK Guys,
itb has the easiest and fastest way to do this. If you have a calculator, you can figure it out in much less time than it would take to log onto Google.
But recall how I did this in the IM: by comparing the front sight to a man sized object at BSZ of 300 yards. And as a couple of you have indicated already, there is going to be some uncertainty or a approximation, here. Especially when the man sized object is assumed to be 20 inches wide.
Let me suggest an alternate way which you may find interesting. Consider a circle of radius r. Then consider a segment on the circumference of that circle of length s. The equation
s=ra
holds, where a is the angle from the center of the circle which subtends the segment, s. But, the angle, a, MUST be expressed in radians. In fact, you may recall the circumference of a circle is given by
c=2(Pi)r
From this, it is easy to see that 2(Pi) radians is equal to 360 degrees.
s=ra can be solved for a,
a=s/r
Therefore, your eye may be considered the center of the circle and the width of the front sight would be the segment, s. And the angle, in radians can, therefore, be found from the above equation. This is really neat because we can convert radians into MOA easily, almost anyway. A milliradian, or (1/1000) radians, is 1 mil on a mil dot scope, and is represented by 3.6 inches at 100 yards. Therefore, we could say that 1 milliradian is 3.6 MOA. Therefore, you could just multiply the value obtained for the angle a times
(3.6 MOA/(1/1000)) radians
to get the value in MOA, which is what we want.
However, this will give you a value a little larger than the method obtained by itb. For example, Instead of 7.9 MOA for his Garand, you would get 8.3 MOA. This is a fairly small amount, and the difference involves the "almost" mentioned earlier. And the reason is that 1 MOA is not really represented by 1 inch at 100 yards. It is something like 1.047???. When this is taken into account, 7.9 MOA will be obtained. But in comparison to other estimates with the front sight, this will be negligible.
But I bring up the equation, s=ra, because. It is a neat equation which can be used to find the distance to a target easily.
If a target, or object, has a known size, that size can be represented by s.
And the distance to that object can be represented by r. And the equation can be solved for r.
r=s/a
If you have a mil dot scope, it is easy to find the number of mils which the target subtends. say x mils. But since this is really milliradians, or mr, and we must express a in terms of radians. The angle a would, therefore, be entered as
(x/1000) radians. And furthermore, r and s must be entered in the same units, say yards.
Therefore, the distance to the target would be given by
r = s/(x/1000)
or
r = s(1000)/x
I love mil dot scopes.
And I hope you haven't fallen asleep.
Incidentally, my Ruger 10/22 with tech sights has a front sight of 7.1 MOA.
I have an M1A NM with 8.2 MOA and a Scout with 5.2 MOA. The strange thing is that both of these front sights are listed as NM, but they have different thicknesses.
"Incidentally, my Ruger 10/22 with tech sights has a front sight of 7.1 MOA.
I have an M1A NM with 8.2 MOA and a Scout with 5.2 MOA. The strange thing is that both of these front sights are listed as NM, but they have different thicknesses."
In other words, NM means nothing when it comes to thickness. Learn something new everyday! :)...O.L.
So, if the front post on my AR is almost 10moa, a 20" target will cover it at 200 yds. This is a big difference from saying you have a 7moa post which brings it to 286 yds or almost 6 clicks in come ups (2 clicks per moa). Do we want to cover this when we teach KD? Or am I just losing my mind here?
This is Andrew. I'd just like to say that you can find the angle measure Don's way except that it doesn't have to be in radians. The formula for finding it in degrees is s=(a)(pi)(r)/180
where s=sector length, a=angle in degrees, and r=radius. You can then divide by 60 to get MOA.
So i guess that the formula for MOA would be s=(a)(pi)(r)/10800 since 180x60 equals 10800. In this second case a would automatically equal the angle measure in MOA.
Please excuse my intrusion into this discussion... DonD is correct with the 20" assumption when calculating for distance...
At Volunteer Training Site - Tullahoma we use both Type E silhouette ( 40" x 20" ) and Ivan silhouette ( 40" x 20" ) targets on the Modified Record Fire Range (MRF) which is a 300 meter pop up qualification range... We also use both target silhouettes when we do a sniper match for one of the events in calculating distance using a mil-dot scope with 12 targets set out from 100 - 1500 meters ( the shooters have to determine the distance of all 12 targets and then hand in their score sheet for this part of the event ) ...
I happen to have both of those targets at the house that I use to teach TN Army National Guard Units Preliminary Marksmanship Instruction before they go to one of our Ranges at their request from Range Control...
Please excuse the mess in my Garage
Type E
(http://i241.photobucket.com/albums/ff63/wickedklown2/M4/target-1.jpg)
(http://i241.photobucket.com/albums/ff63/wickedklown2/M4/target-2.jpg)
(http://i241.photobucket.com/albums/ff63/wickedklown2/M4/target-3.jpg)
Ivan
(http://i241.photobucket.com/albums/ff63/wickedklown2/M4/target-4.jpg)
Ivan in front of the Type E ( I always ask the question to Unit during the PMI Course if they think that the Ivan is not as wide or tall as the Type E and then I show them they are the same...
(http://i241.photobucket.com/albums/ff63/wickedklown2/M4/target-5.jpg)
Sorry I could not add more to the conversation than this...
WK2
WK2, it's good to hear from you again. Thanks for the post. I hope to get down to Smyrna again soon.
And Andrew, you entered the angle a in degrees, but when you multiplied by
(Pi)/180 you converted to radians. When you write s=ra, the a MUST be in radians.
Dart,
With the numbers you give above, the correct value should be 9.8 MOA instead of 9.96. But assuming 10 MOA, this would indeed cover a 20 inch target at 200 yards. But if you are zeroed at 200 yards on the target, there would only be 2 MOA required to go to 300 yards, with the AS come-ups, which would be 4 clicks instead of 6 clicks, according to your post. Or are you confusing horizontal with vertical MOA here? But there are other variables here too. Perhaps everyone doesn't turkey neck like we do. This would change the eye to sight distance. Four more inches would take it to 8.4 MOA. And then too, as stated earlier, it seems like I read somewhere that different AR sights have different sizes. I'm not that familiar with ARs, but that could make a big difference.
Don,
You're right. It should be 4 clicks. I was using the standard 3,3,3,4 when I wrote that instead of the specific AR come-ups. Also, I must have fat fingered the 9.96. It should be 9.76. As for turkey-neck, I do and teach nose to charging handle on an AR. Either way, I am going to teach the 7 moa example but I plan on explaining how to measure your front sight MOA using the pir2 way and give them the google formula as a quick cheat. I'm afraid that if people assume a 7 moa post when they have a 10 moa post, they'll be confused. Kind of like when you have your son help you with your homework.
Quote from: dond on November 25, 2011, 10:08:36 PM
Dart,
With the numbers you give above, the correct value should be 9.8 MOA instead of 9.96. But assuming 10 MOA, this would indeed cover a 20 inch target at 200 yards. But if you are zeroed at 200 yards on the target, there would only be 2 MOA required to go to 300 yards, with the AS come-ups, which would be 4 clicks instead of 6 clicks, according to your post. Or are you confusing horizontal with vertical MOA here? But there are other variables here too. Perhaps everyone doesn't turkey neck like we do. This would change the eye to sight distance. Four more inches would take it to 8.4 MOA. And then too, as stated earlier, it seems like I read somewhere that different AR sights have different sizes. I'm not that familiar with ARs, but that could make a big difference.
I have made an additional calculation which may interest you. As stated earlier,
1 mil at 100 yards is represented by 3.60 inches. And 1 MOA at 100 yards is, in actuality, represented by 1.0472 inches. Therefore,
1 mil = 3.44 MOA,
after rounding off.
And Dart, I knew you did turkey neck and taught it as well. I was thinking of others outside of AS. I would be interested in how the shooters respond to your calculation on the front sight. I suspect it may be too complicated for them, along with everything else they are asked to learn. The simplest thing might be to just mention that it can be calculated from measurements made of the width of the sight and the distance to the eye. And then refer to comparing the front sight to the 1 inch square.
:pop:
they don't put stuff like this in the gun mags. must not be able to fit it in between all the advertisements.
Wow, pop ups with no holes in them. I used to have some of those. @) Now I have to tape paper them to see the new holes.
Junior Birdman used to have a "tool" on an 8.5X11" piece of paper that he'd put up at 25 meters. Everyone then got to lay down and aim their rifle at the piece of paper. It had a tapered target (vertical with smaller width at the bottom) and you'd line the top of your sight up so the corners of your sight "touched" the sides of the taper. There were lines horizontally across the target and they corresponded to the width of your front sight in MOA.
Not sure if that tool was ever saved on the forum here or if its in the instructors took kit somewhere or if its lost. If junior birdman can still be contacted he might be able to e-mail it to someone or put in on the forum himself. It was quick and simple to use right there at the range.
Quote from: Old Dog on November 27, 2011, 09:26:59 AM
Wow, pop ups with no holes in them. I used to have some of those. @) Now I have to tape paper them to see the new holes.
Junior Birdman used to have a "tool" on an 8.5X11" piece of paper that he'd put up at 25 meters. Everyone then got to lay down and aim their rifle at the piece of paper. It had a tapered target (vertical with smaller width at the bottom) and you'd line the top of your sight up so the corners of your sight "touched" the sides of the taper. There were lines horizontally across the target and they corresponded to the width of your front sight in MOA.
Not sure if that tool was ever saved on the forum here or if its in the instructors took kit somewhere or if its lost. If junior birdman can still be contacted he might be able to e-mail it to someone or put in on the forum himself. It was quick and simple to use right there at the range.
That's what I've always done with our "5 spot" drill targets. Color in 2 squares, that's 2 MOA, 6 is six, etc... Works well on scopes to determine cross hair thickness or dot/circle sizes. We've got the tools....O.L.
Junior Birdman's sheet is in the RBC manual.
Here is a digital version that BD made after the Jan VA weekend KD.
http://appleseedinfo.org/smf/index.php?topic=20553.msg161126#msg161126
It replaces a more primitive version that I had which was a scan of JB's version.
Mike
QuoteIn other words, it is more important to know what size your front sight appears to be, to your eye, than it is to know what the front measures, according to the math.
Roger that. For our recent RBC, I created three cardboard cutouts of a 6' man standing (walking towards the shooter), taken directly from a photo that was blown up to represent a good friend of mine (Bob) who got married is no longer allowed to attend anything (long story). If the real "Bob" were to lay out on top of this cut out (affectionately called "Bob Who"< referring to how I respond when asked "Where's Bob?) - it would match nearly perfectly.
I created the cardboard replicas for the express purpose of front site assessment and target detection. The result proves what ItsanSKS has stated above. The math, while more "accurate", becomes moot. It's all about how
your front site looks when placed onto a man-sized target. I know exactly what my front site looks like on target at 100, 200, 300, 400, & 500 yards and so does everyone else that attended the RBC.
Just like standard come-ups vs. real DOPE gathered from shooting at actual distance. The info gleaned on the range in varying light levels, and at different distances is invaluable.
I will freely admit to being old-fashioned and low-tech, but sometimes it works well. I told the shooters at the RBC - what you git from the internet and guys talking at the range isn't always useful (not in those words exactly ^-^).
PH
That's my .02
I have a copy of that in my SB book. I'm going to try it out next time I get to the range.
Quote from: Old Dog on November 27, 2011, 09:26:59 AM
Wow, pop ups with no holes in them. I used to have some of those. @) Now I have to tape paper them to see the new holes.
Junior Birdman used to have a "tool" on an 8.5X11" piece of paper that he'd put up at 25 meters. Everyone then got to lay down and aim their rifle at the piece of paper. It had a tapered target (vertical with smaller width at the bottom) and you'd line the top of your sight up so the corners of your sight "touched" the sides of the taper. There were lines horizontally across the target and they corresponded to the width of your front sight in MOA.
Not sure if that tool was ever saved on the forum here or if its in the instructors took kit somewhere or if its lost. If junior birdman can still be contacted he might be able to e-mail it to someone or put in on the forum himself. It was quick and simple to use right there at the range.
I'm going to make one of these up when I get a chance.
Quote from: PHenry on November 27, 2011, 05:30:50 PM
QuoteIn other words, it is more important to know what size your front sight appears to be, to your eye, than it is to know what the front measures, according to the math.
Roger that. For our recent RBC, I created three cardboard cutouts of a 6' man standing (walking towards the shooter), taken directly from a photo that was blown up to represent a good friend of mine (Bob) who got married is no longer allowed to attend anything (long story). If the real "Bob" were to lay out on top of this cut out (affectionately called "Bob Who"< referring to how I respond when asked "Where's Bob?) - it would match nearly perfectly.
I created the cardboard replicas for the express purpose of front site assessment and target detection. The result proves what ItsanSKS has stated above. The math, while more "accurate", becomes moot. It's all about how your front site looks when placed onto a man-sized target. I know exactly what my front site looks like on target at 100, 200, 300, 400, & 500 yards and so does everyone else that attended the RBC.
Just like standard come-ups vs. real DOPE gathered from shooting at actual distance. The info gleaned on the range in varying light levels, and at different distances is invaluable.
I will freely admit to being old-fashioned and low-tech, but sometimes it works well. I told the shooters at the RBC - what you git from the internet and guys talking at the range isn't always useful (not in those words exactly ^-^).
PH
That's my .02
Here's JB's tool:
Can anyone not see the digital version of the tool that was linked in my reply? The good thing about it is that it was CAD and it is exact. If you use the scanned version of the original you must check it to make sure that the dimensions are correct.
Mike
Quote from: jmdavis on November 28, 2011, 10:43:53 PM
Can anyone not see the digital version of the tool that was linked in my reply? The good thing about it is that it was CAD and it is exact. If you use the scanned version of the original you must check it to make sure that the dimensions are correct.
Mike
I get a "you are not authorized to view this section of the forum" on you link. I would like obtain the digital version.
Here is the Cad version of the tool.
Ok, the same AR that I measured the front post moa to be 9.76 almost covered a sheet of paper (8 1/2") at 100yds. I didn't get a chance to use the cad sheet yet, though. Maybe this weekend.
PHenry is on it. Whatever YOUR sight looks like when compared to a man-sized target at ANY distance is what's important. Who cares if it's 4.76 or 8.79 or whatever. What you're really looking for is "where does my sight cover up that 20" target?"
If you have range available, take a 20" silhouette (or 6' cardboard cutout of Bob) and post it out there somewhere. Back up until your sight is the same size as the silhouette. Range it using a range finder or posted signs at the club, tape measure, whatever. Find out the "exact" distance and then calculate the size of your sight using this formula.
Range = (Target Size in inches/ Sight Width in minutes) X 100
You know your target size is 20" and the distance. Divide it out to find the sight width.
Example - My sight covers up Bob at 250 yards. I know Bob is 20" wide. I take 250/100 and get 2.5. I take 20/2.5 and get 8. My sight is 8 MOA wide.
But that's not what's important. What's important is I know when I look through my sight that it completely covers a man-sized target at 250 yards. If that target is twice as big as my sight then it's at 125 yards. If the target is only 1/2 the size of my front sight, it's at 500 yards.
All I really need to know is can I shoot without a correction or do I need to add some dope. The size doesn't need to be exact for that. We can round and approximate and still be well within 4 MOA, especially considering we're only shooting to 500 yards and most BSZs are at 250/300 already.
Probably the easiest way for us to approximate front sight size is do as oladcock said - color in some squares on the 5-spot targets. We already have four squares colored in for us on each target. Most folks are going to be 50-150% bigger than that. We can add a darkened square or two on each of the 5 square targets and they can go from one target to the next until it matches up. Boom! They know their size.
It would be really easy to have them darken the boxes while you're explaining the concept. As a matter of fact, I'm going to try this at my next event. I'll have shooters leave the center target alone. Top left is 5, top right is 6, bottom right is 7, bottom left is 8. They can fill in the boxes while I'm going over the concept and then we'll post them at 25 and have everyone look through their sights. We'll get a measurement and then test it out on the distance range.
For a KD event this would be very easy to do during sight in. For typical AS weekend events with no KD component we could do this at lunch on Sunday and that would give us an extra trip to walk downrange and get the blood flowing to wake up after a fine meal.
We could get really creative and have an exercise that would require them to measure different targets using only their front sight and then determine the distance to those targets using the formula above. "OK, now you know the size of your front sight.... tell me how far away that simulated 20" target in the upper right corner is. You measured it as 3/4 of your front sight. How far away is it?"
That adds another variable because now they have to figure out how much an extra 25% is. Most of this is probably WAAAaaaaaaaay too advanced for typical AS events, but it's not too hard for IBC/RBC/KD days. Personally, I have a "no math in the field" policy save for my "if it's smaller add some dope if it's bigger shoot it now" rule. Same goes for wind. I'd hate to see shooters out there with their dope book and a calculator trying to calculate 1/2 value 10 mph wind at a target 3/4 the size of their front sight post. Great for RBCs and great for us to learn.... but not necessarily weekend event stuff.
I'll give some of this a shot on Sunday. I'll have the shooters measure their sights using the blocks on the 5-spot target and I'll have the instructors crunch the numbers after hours. I'll let you folks know how it goes.
The 1" squares on the RWVA 25m squares target are 3.5 MOA wide and 3.5 MOA tall IF the target is posted 25m away. Each 1/4" is 7/8 of an MOA at that distance. You could compare your front sight to a 3.5 MOA square and guesstimate from there. Or even color in some of the 1/4" squares to the sides to make a 7 MOA rectangle.
If you know the width of the front post in inches (it may be marked, or can be measured with calipers) then you can do the following:
1) Measure the sight radius, and ADD your eye relief distance to it. Convert this distance to YARDS. (It is the length of two sides of a long skinny triangle, analogous to the target distance (yards) in IMC). = Y
2) Use the measured sight width in inches (the short side of the long skinny triangle, analogous to inches in IMC). = N
3) Use the conversion factor 1.05" per MOA per 100 yards. Use 1.05"/((1 MOA)×(100 yd)) or its reciprocal. In this case your data is (N/Y).
(N/Y)*((100yd)*MOA)/1.05" =(100*N)/(1.05*Y) = sight width in MOA.
There are lots of ways to learn about your front post. Keep it in mind and in view ;)
Like I told the math professor at Gibsonburg several years ago when she was upset that I discouraged people from using fractions.... "When you tell me how I can do 3/8 of a click on my sights, I'll start instructing it that way."
Her reply was 5/4 of people think math is hard. She's correct that we are math-averse in this culture. We're smart, but don't put us on the spot. As such, we should do our best to utilize the K-I-S-S method. We don't need .05s and .79s and EXACT measurements. We need "good enough" to hit 20" targets at 500 yards. With the relatively GIGANTIC margin of error acceptable it's kind of silly for us to split hairs.
I like the fact that we're looking for precision but for Appleseed purposes, is it really necessary?
Instead of splitting hairs on the numbers, why don't we come up with good ways for us to help shooters conceptualize what we're trying to do. Perhaps some drills to aid in mastering the concepts? While they may not be able to precision engineer their shots at 479.2 meters, they will be able to ring steel all day long at 500 yards.
Are we going for perfection in a few shooters or "conceptualizing" in everyone? And probably more importantly... how are we using our time in doing so?
Knowing your front sight width allows you to accurately range distances with your front sight. While not necessarily an "Appleseed" skill, this is an important skill for the rifleman. We spend some time on this at bootcamps and it is one of the more practical lessons that we teach, particularly for hunters.
Another example is kentucky windage At 500 yards a full value 10 mph wind will blow you off the target (7.91MOA), knowing that your sight is 7 (or 8, 9 or 12) moa wide will let you hold (full sight width) or shade (1/2 sight width) the front sight to stay on target. To use these skills you need to both know them and practice them. Knowing that you have an 8 moa sight, a full value 10 mph wind and a 500 yard target can mean this difference between a hit and a complete miss.
You can't focus on the front sight and the target at the same time, so yes, you shouldn't be looking for three significant figures for your front sight width in MOA.
If you spend a lot of time shooting squares at 25m, and you know that that square is 3.5 MOA across, you can get a good sense of how wide your front post is.
If you are really bored and it is raining, you can amuse yourself by doing the math.
Ok, I must not have received the PM changing the size of 1 MOA at 25m. From our Instructor's manual:
"This process is simplified by the one inch square practice targets in current use at
25meters. The one inch squares are placed on a grid of ¼ inch squares. It follows that
each of these ¼ squares represents one MOA."
Here in TN, we've been teaching that each 1/4" square is 1 MOA. Have we been doing this wrong?
Quote from: TN_Dadx5 on December 06, 2011, 02:06:13 PM
Ok, I must not have received the PM changing the size of 1 MOA at 25m. From our Instructor's manual:
"This process is simplified by the one inch square practice targets in current use at
25meters. The one inch squares are placed on a grid of ¼ inch squares. It follows that
each of these ¼ squares represents one MOA."
Here in TN, we've been teaching that each 1/4" square is 1 MOA. Have we been doing this wrong?
I think he is accounting for the difference in 25 yds vs. 25 m. Although I calculate a 1 inch square to be closer to 3.65 MOA at 25 m.
If I didn't shave my head I'd be splitting hairs. Do eyebrows count?
Our 1/4" squares are 1 MOA the same way 500 yards is a 1/4 mile. - And we should continue to instruct it that way.
Quote from: jmdavis on December 06, 2011, 01:18:54 PMKnowing your front sight width allows you to accurately range distances with your front sight. While not necessarily an "Appleseed" skill, this is an important skill for the rifleman. We spend some time on this at bootcamps and it is one of the more practical lessons that we teach, particularly for hunters.
Another example is kentucky windage At 500 yards a full value 10 mph wind will blow you off the target (7.91MOA), knowing that your sight is 7 (or 8, 9 or 12) moa wide will let you hold (full sight width) or shade (1/2 sight width) the front sight to stay on target. To use these skills you need to both know them and practice them. Knowing that you have an 8 moa sight, a full value 10 mph wind and a 500 yard target can mean this difference between a hit and a complete miss.
This is what we need to teach the shooters. Does it matter if their sight is 7.64 MOA or 8 MOA? In practical terms, no. What matters is they master the concept of using their front sight as a field-expedient measuring device.
When we split hairs over a MOA being this measurement or that measurement or worry about front sights being .6 or .8 we're missing the boat on the entire concept we're trying to get across.
... and don't we always leave them with "you should know your rifle/ammo combination and WRITE IT DOWN!!!!"
Quote from: TN_Dadx5 on December 06, 2011, 02:06:13 PM
Ok, I must not have received the PM changing the size of 1 MOA at 25m. From our Instructor's manual:
"This process is simplified by the one inch square practice targets in current use at
25meters. The one inch squares are placed on a grid of ¼ inch squares. It follows that
each of these ¼ squares represents one MOA."
Here in TN, we've been teaching that each 1/4" square is 1 MOA. Have we been doing this wrong?
Pretty close. Close enough for what we're doing I think. But an MOA at 25m is about .29" I think.
Quote from: slim on December 06, 2011, 02:29:35 PM
When we split hairs over a MOA being this measurement or that measurement or worry about front sights being .6 or .8 we're missing the boat on the entire concept we're trying to get across.
Slim, it isn't hair-splitting. Just because we can't, won't, or prudently decide to not use precise numbers in our IMC instruction doesn't mean that we, as instructors teaching each other, have to limit ourselves to the same level of "this is good enough, for you, at this time" approximation. I don't think that this thread is a "how to instruct and no more than that will be allowed" thread.
TN_Dadx5, the 1" square is a little smaller than 1 MOA at 25 yards; it would have to be a 1.05" (1.047") square. Move it further to 25 meters, and it gets even smaller, to 3.5 MOA. Just use the word "approximately" and everything is groovy. For your own knowledge, just keep in mind that a sight adjustment corresponding to 8 of those 1/4" squares is only a 7 MOA adjustment.
If you can't gesstimate the width of your front sight by comparing it to a 3.5 MOA target (or color in a 2" wide at 25m 7 MOA rectangle) the you aren't going to be doing a lot of successful rangefinding past BSZ, but if you can verify that your sight is about the correct BSZ width then you can use it as a go/no-go for man-sized targets within your BSZ zone.
We all have squares targets, and you can use them if you don't have the "front sight MOA" picture. If you've ever used the "FS-MOA" picture, then you know that it can be difficult to choose between different widths off of the picture, i.e. you could very well be off by an MOA. Since we spend so much time with the squares target, I use those instead. The shooters have them in front of them quite a bit, but we don't let them spend much time with the "front sight MOA" diagram.
Quote from: Spanner on December 06, 2011, 03:23:57 PMSlim, it isn't hair-splitting. Just because we can't, won't, or prudently decide to not use precise numbers in our IMC instruction doesn't mean that we, as instructors teaching each other, have to limit ourselves to the same level of "this is good enough, for you, at this time" approximation. I don't think that this thread is a "how to instruct and no more than that will be allowed" thread.
Good point. This isn't the instructor thread, this is the public knowledge thread. As such, you are correct. You can talk all day long about whatever you'd like. But, is that what we do on the AS forum?
Not trying to be debbie downer here and I'm definitely not knocking anyone for being precise. I'm simply making the point that as it relates to Appleseed, this isn't helping anyone. The question has been answered and several pretty decent ways of "figuring it out" have been presented.
Anything further IS splitting hairs and when the noobs come along to figure out how to use their front sight we have them doing trig problems instead of simple, field-expedient methods that a rifleman uses. We're not shooting 10x at 1,000. We shoot 4 MOA at 500. As you've pointed out, it's a go/no-go standard and we've already gone ahead.
Slim and Spanner,
Thanks for the info, I'm glad that I'm not teaching wrong (I'm ok not teaching exact). I've been shooting for a long time but never got involved in the detailed math behind it. This thread has been helpful in another way. After calculating my AR-10's front sight, I was wondering why they would make it just off at each 10 yards. Then I reread the thread and added my eye relief and its pretty much dead on 100 yd when the target appears as wide as the front sight.
Charlie
All the front sight stuff is nice but you should be able to do it without the sight, too. I can remember getting into arguemtents with my hunting/shooting buddies about "how far away is that ground hog?" Sometimes they are standing up, sometimes they are horizontal and feeding, sometimes they are nervous and you can only see a small part of their head. If you want to hit the head (there is no other target but the head unless you just like making a mess) you have to be able to look at the target, look at various items around the target and judge (guess accurately) the range as you'll have to hold over/under based on the range. I must have been pretty good at it as I rarely missed and I only hit one below the head in three years.
Practice. Take a walk. Pick a target. Estimate the range. Walk it out and see how far the target really was from your starting point. Repeat it till you're good at it. Used to work for me.
You can't replace inches/minutes/clicks with the above but its a good thing to be able to do.
Quote from: Old Dog on December 06, 2011, 06:50:11 PMPractice. Take a walk. Pick a target. Estimate the range. Walk it out and see how far the target really was from your starting point. Repeat it till you're good at it. Used to work for me.
Excellent suggestion!
If you folks don't know your "pace count" then you should learn it. Go to a football field and walk the hundred yards. (110 for meters.) Count how many paces (every left foot) it takes. Do the same thing on rough or uneven ground. Get a good number for you.
Then, when you're out hunting you can pace it off to landmarks. "That big tree is 140 yards. The base of the little hill is 365. The creek is 490."
Using pre-determined distances IS an Appleseed-related skill and part of our KD lesson. It's something all of us should know how to do and it will also reinforce using the front sight as a double check. "I paced it off as 395 and my front sight tells me it's just a shade under 400. If my target is there I'll add five clicks and be dead on."
Quote from: slim on December 06, 2011, 01:01:49 PM
Like I told the math professor at Gibsonburg several years ago when she was upset that I discouraged people from using fractions.... "When you tell me how I can do 3/8 of a click on my sights, I'll start instructing it that way."
Her reply was 5/4 of people think math is hard. ...
Slim: "She" was upset? "Her" reply? You mean there's a math-professor chick frequenting the Appleseeds at my home range? Cool! ;)
JMD: I liked the stuff we did at bootcamp, using frontsight to estimate range on a target of known size. The tool you're talking about seemed elegant in its combination of effectiveness and simplicity.