Any information on how to calculate MOA? - DFWstangs Forums
 
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post #1 of 23 (permalink) Old 04-25-2010, 09:49 PM Thread Starter
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Any information on how to calculate MOA?

Browsed a bit on google, but didn't find a direct answer.

Today I shot a total of 5 rounds at 100 yards to try and group them up. How would I calculate the MOA?
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post #2 of 23 (permalink) Old 04-25-2010, 09:53 PM
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1 MOA = 1 inch at 100 yards.
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post #3 of 23 (permalink) Old 04-25-2010, 09:59 PM
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What Matt said.
When you hear about "sub-MOA" groups, that means less than 1" groups at 100, less that 2" at 200, etc.
Did you go again today?
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post #4 of 23 (permalink) Old 04-25-2010, 10:01 PM
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Take the five rounds and measure their circumference.

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post #5 of 23 (permalink) Old 04-25-2010, 10:03 PM
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The proper measurement is center to center of the 2 holes farthest apart. You get this by measuring outside to outside of the 2 holes farthest apart and subtracting the caliber of the gun from your measurement. I use a dial caliper to measure groups. It makes the math easier.

I copy/pasted this because I was too lazy to type it myself.
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post #6 of 23 (permalink) Old 04-25-2010, 10:10 PM Thread Starter
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Quote:
Originally Posted by helosailor View Post
What Matt said.
When you hear about "sub-MOA" groups, that means less than 1" groups at 100, less that 2" at 200, etc.
Did you go again today?
Yea, I took my sister out there so she could shoot my handgun for the first time. I shot a bullet that hit the hole if my previous shot today too! I bought more Fiochhi v-max 40 grain and it shoots flawlessly.

Quote:
Originally Posted by 03trubluGT View Post
The proper measurement is center to center of the 2 holes farthest apart. You get this by measuring outside to outside of the 2 holes farthest apart and subtracting the caliber of the gun from your measurement. I use a dial caliper to measure groups. It makes the math easier.

I copy/pasted this because I was too lazy to type it myself.
That's jacked up! So all the shots that are extremely close to each other mean nothing eh. I grabbed a take measure as that's all I have, the farthest two are 7/8".
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post #7 of 23 (permalink) Old 04-25-2010, 10:17 PM Thread Starter
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Found a picture of the previous owner's grouping at 100YDs with his hand loads.

Guess if I really want to improve I need to hand load and stay consistent with my trigger pull and breathing.

This is fun!
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post #8 of 23 (permalink) Old 04-25-2010, 10:18 PM
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Quote:
Originally Posted by Skidmark View Post
Yea, I took my sister out there so she could shoot my handgun for the first time. I shot a bullet that hit the hole if my previous shot today too! I bought more Fiochhi v-max 40 grain and it shoots flawlessly.



That's jacked up! So all the shots that are extremely close to each other mean nothing eh. I grabbed a take measure as that's all I have, the farthest two are 7/8".
Details on the rig? .78moa is good for a beginner.

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post #9 of 23 (permalink) Old 04-25-2010, 10:26 PM Thread Starter
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Details on the rig? .78moa is good for a beginner.
Remington 700 SPS tactical .223
Hogue stock
Nikon 6-18x40 Buckmaster
Harris bi-pod
Per previous owner trigger pull is at 1.5lbs

Shooting the Fiochhi extrema v-max 40 grains, had good luck with them...
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post #10 of 23 (permalink) Old 04-25-2010, 10:31 PM
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1 minute = 1/60 degree, so sub-MOA means the angle formed by your two outermost shots and your rifle (your rifle is at the vertex) is less than one sixtieth of a degree.

Using basic trig, you can find that the ratio of the distance between shots, d, to the distance you're shooting at, D (measured in the same units), is equal to the sine of 1/120 degrees.

d/D = sin (1/120) ~ 1.45x10^-4
d = D sin (1/120) ~ D * 1.45x10^-4

So at 100 yards (3600 inches), a distance of 1.045" between shots is 1 MOA.

I thought you, being Asian, would be better at math.


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post #11 of 23 (permalink) Old 04-25-2010, 10:34 PM
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That's pretty good for a factory rifle. I don't think the SPS hogues come with the aluminum bedding block, but they're pretty nice all the same. Also, Remington 700's have a little bit of free bore. You might try some Federal Gold Medal Match. A lot of companies are building their guns with that in mind. No matter what you do, though, hand loading will do a LOT to make your gun accurate. Have fun, man!

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post #12 of 23 (permalink) Old 04-25-2010, 10:35 PM Thread Starter
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Quote:
Originally Posted by That_Is_My_El_Camino View Post
1 minute = 1/60 degree, so sub-MOA means the angle formed by your two outermost shots and your rifle (your rifle is at the vertex) is less than one sixtieth of a degree.

Using basic trig, you can find that the ratio of the distance between shots, d, to the distance you're shooting at, D (measured in the same units), is equal to the sine of 1/120 degrees.

d/D = sin (1/120) ~ 1.45x10^-4
d = D sin (1/120) ~ D * 1.45x10^-4

So at 100 yards (3600 inches), a distance of 1.045" between shots is 1 MOA.

I thought you, being Asian, would be better at math.
Yea that is like a foreign language. My main concern was do I only calculate the farthest shots or compensate for all 5 shots somehow, but that was answered above!
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post #13 of 23 (permalink) Old 04-25-2010, 10:41 PM Thread Starter
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Quote:
Originally Posted by Yale View Post
That's pretty good for a factory rifle. I don't think the SPS hogues come with the aluminum bedding block, but they're pretty nice all the same. Also, Remington 700's have a little bit of free bore. You might try some Federal Gold Medal Match. A lot of companies are building their guns with that in mind. No matter what you do, though, hand loading will do a LOT to make your gun accurate. Have fun, man!
http://www.snipercentral.com/spstactical.htm mentioned two aluminum pillars, but definitely no bedding. I was browsing stocks last night, but i'm unsure how much they'll improve my shot. I wouldn't mind something with a thumb hole though, I think I would be more comfy.

I give the federal gold match a shot! My buddy has a complete setup for a .223 so I might try to see if he'll let me use his equipment. I have the load data for the above bullets that the previous owner shot at. Some people say they are pretty hot though.

Previous owner modified the magazine to hold 2.450 oal amax. 23grains of ramshot tac, cci primmers, 75 grain amax, 2.450 OAL
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post #14 of 23 (permalink) Old 04-25-2010, 10:49 PM
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here's the formula I use in MS Excel to determine MOA of a given group:

=60*2*(ATAN((A4/2)/(B4*36))*180/PI())

In the case of this exact formula, the group size goes in A4 and the distance in yards goes in B4. Just change the A4 and B4 to whatever cells you want. Copy it & paste it in and it'll start working for you right away. You may have to change the cell references if you have the "R1C1 reference style" set in Excel.

Enjoy.

For the technically minded, you can use the trig functions for a right triangle if you take the isoceles triangle formed by the bore and the group size and split it in half longwise to get two right triangles. Do the trig on one to get 1/2 the MOA, and double it. The tangent of the 1/2 grouping angle is opposite (1/2 the group size) over the adjacent (distance in yards). Use arctangent to get the angle, then do the stuff excel requires to convert from radians to minutes of angle, and bam!, there you are.

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post #15 of 23 (permalink) Old 04-25-2010, 10:54 PM Thread Starter
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Quote:
Originally Posted by gonecampin View Post
here's the formula I use in MS Excel to determine MOA of a given group:

=60*2*(ATAN((A4/2)/(B4*36))*180/PI())

In the case of this exact formula, the group size goes in A4 and the distance in yards goes in B4. Just change the A4 and B4 to whatever cells you want. Copy it & paste it in and it'll start working for you right away. You may have to change the cell references if you have the "R1C1 reference style" set in Excel.
Thanks Jon!

I am stuck using excel for work all the time and this makes it actually fun. I tried it out and it worked nicely
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post #16 of 23 (permalink) Old 04-26-2010, 11:09 AM
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The oal from the handloads is something that helps accuracy alot. The stock on your Remington should be just pillar bedded unless the previous owner glass bedded also which would also help.
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post #17 of 23 (permalink) Old 04-26-2010, 10:31 PM
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No problem.

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post #18 of 23 (permalink) Old 04-27-2010, 12:05 AM Thread Starter
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The oal from the handloads is something that helps accuracy alot. The stock on your Remington should be just pillar bedded unless the previous owner glass bedded also which would also help.
I made a couple purchases today, hopefully my personal skill will catch up to the rifle's potential. I didn't think i'd enjoy shooting this bastard this much, so I may have to re-invest in a loading setup.

Anyways, ordered a Bell and Carlson adjustable "tactical" medalist A5 stock and the Badger trigger guard with detachable magazine. Can't wait to get everything put together
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post #19 of 23 (permalink) Old 04-27-2010, 05:40 PM
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This is what we did for an informal match last summer.

Using a digital micrometer, measure the outsides of the two furthest bullet holes in the group and subtract half the diameter of the bullet. Measure at the black ring (residue) of the bullet going through the paper.

I got the Frankford Arsenal micrometer for about $19. You can get them at toolshops.

If you scan your target in. You can use OnTarget software to do the work. It is shareware/freeware.
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post #20 of 23 (permalink) Old 04-27-2010, 06:04 PM
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Yo Brien, I've got a digital micrometer if ya need it.
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post #21 of 23 (permalink) Old 04-27-2010, 06:47 PM
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Originally Posted by Skidmark View Post
I made a couple purchases today, hopefully my personal skill will catch up to the rifle's potential. I didn't think i'd enjoy shooting this bastard this much, so I may have to re-invest in a loading setup.

Anyways, ordered a Bell and Carlson adjustable "tactical" medalist A5 stock and the Badger trigger guard with detachable magazine. Can't wait to get everything put together
Does the new stock come with a full bedding block or just pillar bedding blocks.
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post #22 of 23 (permalink) Old 04-27-2010, 06:57 PM Thread Starter
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Originally Posted by helosailor View Post
Yo Brien, I've got a digital micrometer if ya need it.
Bring it out next time and we'll tinker w it!

Quote:
Originally Posted by GT98SVO View Post
This is what we did for an informal match last summer.

Using a digital micrometer, measure the outsides of the two furthest bullet holes in the group and subtract half the diameter of the bullet. Measure at the black ring (residue) of the bullet going through the paper.

I got the Frankford Arsenal micrometer for about $19. You can get them at toolshops.

If you scan your target in. You can use OnTarget software to do the work. It is shareware/freeware.
I do indeed have a scanner, checking out that software now

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Originally Posted by dee View Post
Does the new stock come with a full bedding block or just pillar bedding blocks.
It's full aluminum bedding, the detachable mag is probably going to take some work to fit. I hit up CJ, so he's going to take a peek at it once I get all the parts in.
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post #23 of 23 (permalink) Old 04-27-2010, 07:52 PM
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It's full aluminum bedding, the detachable mag is probably going to take some work to fit. I hit up CJ, so he's going to take a peek at it once I get all the parts in.
Yea alot of those new bottom parts take some fitting to work.
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