38 comments on “AR-15 — Methods For Zeroing A2 Type Sights

  1. OUTSTANDING procedures that ALL others I’ve read (and failed) are completely confusing not to mention even if one isn’t familiar with BDC sights that’s obviously wrong. Now maybe I’ll really start using my le6920 across the course and know this site as goood as my M1A’s. THANKS again.

    Liked by 1 person

    • Kick ass. I’m glad that it helped. I had a 20″ Colt HBAR for 15 years and I never really understood the nuances of the sight system. After all of this research and experimenting I hate that I sold it. I now have a 16″ Smith & Wesson M&P Sport that I purchased so that my kids could wear out the barrel with steel case ammo and .22LR with a conversion kit. I put a Rock River Arms A-2 sight on it and set it up with the Revised Improved BZ Method. I have an exact setting for 25 meters (I can’t shoot enough to tell a difference at 25 yards), 50 yards, and 100 yards. I can then put it on the “3” or “4” setting and hit steel targets at 300 and 400 yards. I’m pretty sure that I’m making occasional 500 yard hits, but 5.56mm doesn’t hit the steel hard enough at that distance to be heard very well. The next time that we are shooting it at the range I’ll have someone spot it for me and let me know if I’m getting hits.

      Please keep us posted how it works for you.

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  2. Fantastic article on the sighting options! It is a one stop shop for dialing in the irons. I have some questions on the 20 inch rifle running the RIBZ zero. If you set rear sight knob at “Z” setting for the 25 meters (27 yards) sight in, wouldn’t the 25 and 300 meter adjustment = “Z” setting instead of 25 meters = “Z” and 300 meters = 6/3 setting? Sorry too many years of shooting the A2 8/3 with Army’s 25/300 meter BZO. Trying to learn some new dope with that goofy 6/3 knob on an 20 inch rifle is a bit confusing at the moment. Thanks for taking time to write such a detailed and very helpful article.

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    • Hi, Jerry.

      I’m glad that you found it helpful. It took a lot of research and experimenting to put it all together.

      To answer your question, the ONLY time that you use the “Z” setting is when you are zeroing a 20″ barrel rifle with a removable carry handle at 25 yards. When a 20″ rifle and removable carry handle combination is properly zeroed so that the bullets impact at point-of-aim at each setting (300 meters with the “3”, 400 meters with the “4”, etc.), then the near zero with the 6/3 setting is not 25 meters like it is with a 20″ barrel and fixed carry handle. It is somewhere around 31 meters. The “Z” setting lets you still use a 25 meter range and targets and properly zero your 20″ barrel and removable carry handle combo.

      Any time that you would practice with your rifle on a 25 meter range, then you would use the “Z” setting, but that would be the only time.

      Let us know how that works out for you.

      SA

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  3. More of a question then anything else, I use a cross hair front sight post instead of the issued post. Would the formula change & if so, how? P. S. 16″, 55 gr. fixed carry handle.

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  4. Great article, clearly written and easy to understand. I read the entire essay after spending the better part of a day struggling with partial descriptions, generic terms and a general lack of specific information on barrel length, sight distance or ammunition type. Most sources only refer to 20” rifles or refer to M4 carbine with no barrel length specified or only 14.5”. I have a Rock River Arms Mid Length A4 with a 16” barrel so your specific explanations with regard to barrel length, sight distance and ammunition were greatly appreciated. I also appreciated the background philosophy behind each sighting method. Yours was the only source I found that brought all the techniques together comparing them and explaining the differences. I have friends with a variety of different AR-15 configurations so I will be sharing your experience with them also. Thanks for your work in sorting out all the details.

    Liked by 1 person

    • You are very welcome. I hope that it helps you out. I was very confused when I first started researching the subject. Everyone is an expert on the subject, and yet I’ve never been able to get anyone to explain why they do it that way (“that is the way we did it in ‘Nam”, or “that is the way we did it in the Corps”. Not explanation why they did it that way, or what results you could expect by doing it that way.

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    • The ONLY time that you use the “z” is with a rifle with a 20″ barrel and removable carry handle while zeroing at 25 meters. If you modify you sight as with the Santos method, you can still zero with the “z” at 25 yards with a 20″ barrel. You do not every use the “z” setting with the USMC method because they are setting their rifles up for yards.

      Confused yet?

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  5. I would like to sight in my A2 using the Santos method. I have one point I am confused on. When doing the sighting in adjustments at 50 yards I understand I will be using the front sight post to raise or lower the strike of the projectile but which rear sight aperture will I be using? If I am reading it correctly the small aperture will be flipped down and I will be using the 0-200 large aperture.

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  6. So I have a Colt 727 clone. 14.5 barrel and a A2 8/3 fixed rear… What do I set the rear sight clicks at to do the Army 25/300 zero?

    You cover 20″ fixed, and 14.5 detachable but not 14.5 fixed.

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    • Geez… that is a rare combination… Blackhawk Down style.

      I would set it to the 8/3 setting and zero at 25 meters (27.3 yards) with 62 grain ammo.

      You won’t use the “z” setting because that is only used with 20″ barrels to compensate for the increased projectile velocity that you enjoy from a longer barrel.

      Do you have a 100 meter (109 yard) rifle range to verify zero? After zeroing at 25 meters with the 8/3 setting your rounds should hit 4.6″ high at 100 meters.

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      • “Blackhawk Down style” That was exactly what I was going for!

        I do have a 100m range will try the normal 8/3 at 25m. Thanks!

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  7. Came back to use these instructions again after finding it and using it for me LE6920 (it WORKS). Again, this is by far the best most carefully written zeroing procedure out here. Molon did a good job, but when you throw in 50-100 of guys with different definitions of A1/2/3/4, then different barrel lengths often not referenced, bullet weights not referenced against the the drop charts and assumed in thread/questions, FS post heights, and more (less)… then throw it all together, what you get is guys thinking they “got it”. These AR15, M4 sights, subtle differences between different models can be damn tricky. They sure as hell are compared to my M1A’s which which are a snap to zero when the barrel/s are properly indexed to the gas ports which John Garand, H&R, SA, TRW, WIN had down. The sights the byproduct of a mechanical engineering genius who designed those sights for dimwits like me. Savanah here via this right up gets the AR equal to that procedure that I printed off and shared with several guys each after using it echoing me exact sentiments. THANKS AGAIN.

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    • Sorry that I took so long to reply. Christmas, kids, work, etc.

      It’s not too hard. Watch this video. All you will need is a small allen wrench (size described in the video). Just be careful not to back the screw out too far.

      Before you start to work on adjusting your sights like the Marines, I suggest that you buy a box of crayons to eat while you work on your rifle.

      Remember for the USMC method you will need to adjust a fixed carry handle’s sights (8/3) where it bottoms out 2 clicks below the 8/3 setting, and if it is a removable carry handle with a 6/3 setting then you will need to adjust it so that it bottoms out 4 clicks below the 6/3.

      20″ barrel with fixed carry handle?: Set the sights for the lower 8/3 and zero at 36 yards with M855 (37 yards with M193). Use the same setting to very zero at 300 yards. Then dial the rear sight down 2 clicks below the 8/3 setting (bottomed out if you adjusted it correctly) and verify zero at 56 yards and 200 yards.

      20″ barrel with a removable carry handle? Set the sights for the lower 6/3 and zero at 36 yards with M855 (37 yards with M193). Use the same setting to very zero at 300 yards. Then dial the rear sight down 4 clicks below the 6/3 setting (bottomed out if you adjusted it correctly) and verify zero at 56 yards and 200 yards.

      16″ barrel with removable carry handle? Set the sights for the lower 6/3 and zero at 33 yards with M855 (30 yards with M193). Use the same setting to very zero at 300 yards. Then dial the rear sight down 4 clicks below the 6/3 setting (bottomed out if you adjusted it correctly) and verify zero at 56 yards and 200 yards.

      Good luck. Let us know how it works out for you.

      Semper fidelis.

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  8. Great info!!! I just purchase 16” carbine 1-7 twist with a p.s.a. carry handle. My question is for the RIBZ zeroing….. all I have to do is the 1-mechanical zero 2- zero at 27 meters but modify rear site 6 clicks below the 6/3 while I zero rifle at 27 meters using 55 grain. Thanks!!!!please help

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    • I’m not really sure what you are asking. All we are trying to accomplish is to modify the sight so that we will have a setting to use on 50 and 100 yard rifle ranges. To accomplish this you modify the rear sight so that you can dial it down six clicks below the 6/3 setting.

      You will then zero the rifle as normal at 25 meters with the 6/3 setting (300 meters setting).

      You should now be able to hit targets at 50 yards with the sight set four clicks below the 6/3 setting, and 100 yards with the sight bottomed out with six clicks below the 6/3 setting.

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  9. Holy damn dude. I can’t tell you how much I appreciate what you’ve made here. You know, all these years I thought those sights were set for yards. So glad you posted the armorer’s mod, too. I’ll send you a box of my favorite flavored crayons. Thank you.

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  10. I’m confused on what initial zero to use. I have a 16″ 1/7 midlength gas with carry handle. I’ve modified the rear sight -6 clicks from 6/3. So I zero it at 25 meters/yards with 62 grain correct? How about 55? Thanks for the get back.

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    • Just zero it perfectly at 25 meters with the lower 6/3 setting. On that setting it should hit where you aim at 25 meters and 300 meters. If you are shooting at 50 yards then dial it down 4 clicks below the 6/3, and if you are shooting on a 100 yards range then dial it down 6 clicks below the 6/3 (bottomed out). If you really want to be picky, then do it with 62 grain ammo. I doubt that you will notice too much difference between 55 and 62 until you start shooting really far out.

      Like

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