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MOA/ Click type question

 
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  #1  
Old 06-10-2009, 09:30 AM
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MOA/ Click type question

For some reason my brain isn't cooperating with me today. I went out this morning to do a trajectory validation and check my spin drift but it was so foggy I couldn't see past 100 yds. So I decided to try to find out the actual click value of my scope. Didn't want to waste the trip and had to go to work.

Here is the info:

Distance to target 107 yards
advertised click value of scope 1/4 MOA per click

I shot a 3 shot group at my zero dot then I dailed 28 MOA up and shot 3 more.

From center to center (top group to bottom group) I have 30 9/16"

What the heck is my actual click value?
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  #2  
Old 06-10-2009, 10:54 AM
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Re: MOA/ Click type question

I'll take a crack at it.

At 107 yards, 1 MOA=1.07"

you have 30 9/16" or 30.5625"

(Sorry, I'm an engineer by trade and prefer to work in decimals)

30.5625"/1.07"=28.5631 MOA

If you dialed up 28 MOA that means you went up 112 clicks on your scope (28 MOA X 4 clicks per MOA)

If you actually got 28.5631 MOA that means that each click was worth .255 MOA

By this reasoning The actual MOA/click value is .005 MOA greater than advertised.

If this is correct than at 1000 yards each click would give an additional .05" of elevation above the 2.5" that 1/4 MOA would be.

This is also assuming that MOA means 1" at 100 yards. I know there's some other definitions out there but that's another issue.

I hope someone double checks me on this.
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Old 06-10-2009, 11:32 AM
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Re: MOA/ Click type question

406Pat, pretty close.

You needed to use 1.047" for MOA at 100yds, which gives 1.12029"/moa at 107yds

28moa*1.12029=31.37

Spread of group is 30.5625" for a difference of .81" or .72moa difference.

If the gun and shooter were perfect, then the scope would be off by .72MOA, however I don't know how large the groups are. Unless the gun and shooter are both worldclass (less than 1/4moa group sizes), then I would trust the scope.

AJ

ps: Hopefully, someone will double check my calcs.
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Old 06-10-2009, 11:39 AM
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Re: MOA/ Click type question

Quote:
Originally Posted by 406pat View Post

This is also assuming that MOA means 1" at 100 yards. I know there's some other definitions out there but that's another issue.
1" at 100 yards is referred to as "Shooters MOA".

True MOA (Minute of Angle) is 1.047" (rounded) at 100 yards. To get this number take the tangent of 1 min (or .0166666 degrees) and multiply that by the distance in inches.

At 107 yards a true MOA is 1.121" (rounded) at 100 yards

Some scopes dial Shooter's MOA others true MOA.

It looks like yours is Shooters MOA. The .005 difference per click in advertised value that 406Pat got using a Shooter's MOA is very close. The difference is most likely due to group variance and measuring error.

Shoot more groups, re-calc, and see what you get next time.


Paul
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Old 06-10-2009, 01:07 PM
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Re: MOA/ Click type question

Quote:
Originally Posted by AJ Peacock View Post

If the gun and shooter were perfect, then the scope would be off by .72MOA, however I don't know how large the groups are. Unless the gun and shooter are both worldclass (less than 1/4moa group sizes), then I would trust the scope.

AJ

Defiantly not the case. However If I understand what your saying. Then there's not enough error for me to worry about, right? The bottom group was .75MOA and the top one was .2 (probably the best group I ever shot oddly enough). The gun is a 270 win.

So what does being off .72MOA make my click value, .18846? (.72x1.047=.75384/4=.18846)

What ever I get here for error is likely me. Just curious what you guys come up with.
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Old 06-10-2009, 01:14 PM
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Re: MOA/ Click type question

Quote:
Originally Posted by jmason View Post
Defiantly not the case. However If I understand what your saying. Then there's not enough error for me to worry about, right? The bottom group was .75MOA and the top one was .2 (probably the best group I ever shot oddly enough). The gun is a 270 win.

So what does being off .72MOA make my click value, .18846? (.72x1.047=.75384/4=.18846)

It would be (error)/(adjustment) or .72/28 or 2.571% error. Assuming you had shot it perfectly, that would make each click 1.047/4*1.02571=.2685moa.

However, with only a single test, it is likely that your group center isn't actually the center of a larger sample size. If the center of the second group was actually at the top of the group, then your error would be reduced by .75/2 = .375, leaving an error of .72-.375 = .355. If the smaller group center was at the edge, that could reduce your error another .1moa.

I would personally trust the scope, unless you can duplicate the measurement several more times. My guess is that your scope is very close (close enough to ignore).

AJ
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Last edited by AJ Peacock; 06-10-2009 at 01:18 PM.
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  #7  
Old 06-10-2009, 01:22 PM
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Re: MOA/ Click type question

Thanks AJ. Thats what I was lookin' to hear.
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