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Mechanical zero setting for M1A

This is a discussion on Mechanical zero setting for M1A within the Accuracy forums, part of the M14 M1A Forum category; My current windage zero is six clicks left of the reference line on the back of the rear sight. My understanding is that the mechanical ...


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Old February 24th, 2017, 05:43 PM   #1
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Mechanical zero setting for M1A

My current windage zero is six clicks left of the reference line on the back of the rear sight. My understanding is that the mechanical zeroing process involves setting the windage index dead even on the rear sight reference line then loosening the front blade set screw and manually moving it as needed to get the impacts on target.

First, Is my understanding of this procedure correct. I know the direction of movement is in the same direction as the misplacement of the shots. It's like with an AK front site adjustment. Second, what is the traditional range for such zeroing? Never done a mechanical zero before.

Regarding elevation my understanding is that you sight it in for 25 yards and that will also work for 200 yards? Am I right on that one? Once that is done set the elevation drum for the "2" line.

Grateful for any feedback on this.

Regards,
Bill

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Old February 24th, 2017, 06:16 PM   #2
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You have approximately 32 clicks of windage, 16 left and 16 right. You can center your rear sight base on the line, but the middle line isn't always in the center of the receiver. You can align the top edges of the rear sight base with the ears on the receiver itself, if that helps you get to a mechanical zero.

Battlesight zero is 250 meters, the long line between the 2 and 4 on the elevation drum. Your impact at 25 meters needs to be 4.6 centimeters above point of aim.

Read Chapter 3 below:

https://archive.org/stream/FM23-71#page/n47/mode/2up

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Old February 24th, 2017, 06:55 PM   #3
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You should have a front sight centerline which you should set up first. My Norinco was way off. Then sight in the rear sight for windage and elevation. If you run out of windage adjustment then you'll need compensate with the front sight adjustment. Hint: make sure your front sight is not bent.

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Old February 24th, 2017, 07:16 PM   #4
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Quote:
Originally Posted by KurtC View Post
You have approximately 32 clicks of windage, 16 left and 16 right. You can center your rear sight base on the line, but the middle line isn't always in the center of the receiver. You can align the top edges of the rear sight base with the ears on the receiver itself, if that helps you get to a mechanical zero.

Battlesight zero is 250 meters, the long line between the 2 and 4 on the elevation drum. Your impact at 25 meters needs to be 4.6 centimeters above point of aim.

Read Chapter 3 below:

https://archive.org/stream/FM23-71#page/n47/mode/2up
OK I'll give it a try. Hopefully there's a video somewhere of someone doing it.

Thanks
Bill

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Old February 24th, 2017, 07:23 PM   #5
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My polytech mechanical zero has my front sight almost hanging off the right side. It looks goofy but it works. You are correct that the centering mark is centered then adjust front sight to get zero.
Bob

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Old February 24th, 2017, 09:02 PM   #6
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My Springfield NM Garand's front sight is exactly even with the right side of the mounting flat. It looks a bit odd but it is dead on for windage.

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Old February 25th, 2017, 05:35 AM   #7
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Badger5th,

I'll take it that your "6 clicks" are full minute value and your not referring to a NM sight which is 1/2 minute. You are correct in the direction to move the sight and if you have a depth mic or a dial caliper you need to move the front sight .008 for each minute. Just check from the front sight mount to the sight base and adjust accordingly.

John

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Old February 25th, 2017, 06:26 AM   #8
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You should first mark the front sight with some sort of witness line to show where it was located when you zeroed using the rear sight.

THEN, just move the front sight the same distance that the rear sight shows from the rear sight's mechanical zero.

Jay Kosta
Endwell NY USA

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Old February 25th, 2017, 06:33 AM   #9
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Originally Posted by Badger5th View Post
OK I'll give it a try. Hopefully there's a video somewhere of someone doing it.

Thanks
Bill
You don't need a video. The manual above has plenty of pictures and is written with draftees in mind. It's the clearest and most concise explanation of zeroing.

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Old February 25th, 2017, 07:05 AM   #10
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As jay said you need a witness line across front sight and base. I use a very small dab of white paint. When the sight gets moved you can easily see the displacement. For reference moving the width if a .5mm mechanical pencil lead is about .008 as Dstrflman suggested will move impact about an inch.

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Old February 25th, 2017, 07:45 AM   #11
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FS to one side.

Quote:
Originally Posted by ripcord View Post
My Springfield NM Garand's front sight is exactly even with the right side of the mounting flat. It looks a bit odd but it is dead on for windage.
Having that situation always annoyed me. Your situation, if I remember correctly, indicates the barrel is under- screwed.. That is the best situation of the two, much easier to fix.. The barrel draw is a guessing game regardless of the equipment used.. Over the years I have seen one M14, just barreled, that had a windage of MZ on first firing.. Three clicks was normal.. Art

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Old February 25th, 2017, 12:43 PM   #12
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Quote:
Originally Posted by KurtC View Post
You have approximately 32 clicks of windage, 16 left and 16 right. You can center your rear sight base on the line, but the middle line isn't always in the center of the receiver. You can align the top edges of the rear sight base with the ears on the receiver itself, if that helps you get to a mechanical zero.

Battlesight zero is 250 meters, the long line between the 2 and 4 on the elevation drum. Your impact at 25 meters needs to be 4.6 centimeters above point of aim.

Read Chapter 3 below:

https://archive.org/stream/FM23-71#page/n47/mode/2up
That is a very informative read. For anyone interested I took the formulas in the manual and turned them into a spreadsheet. Not sure how accurate it will be but when I get my rifle and go to the range to zero it I figure I will take this with me and see if it will help.
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File Type: jpg M-14 Iron Sight Quick Refrence.JPG (104.6 KB, 32 views)

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Old February 25th, 2017, 04:59 PM   #13
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Thanks all for your help and feedback. I went the range today and got it done.

I followed the general procedure in the FM 23-71 except that I used a standard 50 foot pistol target at 25 meters with reference lines drawn on it. The horizontal line in the attached photo is exactly 4.6 cm (per FM 23-71) above the six o'clock point on the aiming black. Used a 6-hold as I am accustomed to shooting. Finally set the elevation drum for the 250 meter battle zero line.

Got the front sight drifted perfectly after three adjustments.

Went to hundred yard line, dropped rear elevation one MOA. Left the windage alone. Ten shot group dead center on target. Crappy group size (3-inch) but it was balls on centered. Used XM80 ball for all zeroing and test firing at 100 yards. Now the fun can finally commence.

Thanks again.

Regards,
Bill
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File Type: jpg M1A BZO.jpg (168.2 KB, 29 views)

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Old February 25th, 2017, 05:39 PM   #14
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Good looking group there, Badger. Enjoy the fruits of your labor. Try some really good ammo and you may be suprised how well your rifle shoots-Federals Gold Metal Match or OTM.

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Old February 25th, 2017, 07:02 PM   #15
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Quote:
Originally Posted by boomerpusher View Post
Good looking group there, Badger. Enjoy the fruits of your labor. Try some really good ammo and you may be suprised how well your rifle shoots-Federals Gold Metal Match or OTM.
Believe me I know that. While I'm relatively new to the M1A platform I'm a pretty old hand at reloading, been doing it for 25 years. I'll be rolling some match grade stuff and going out again next weekend. BTW I always use XM80 ball and 168gr FGMM as bench marks for comparing my hand loads.

Regards,
Badger

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