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[ARCHIVED THREAD] - A2 zero

Posted: 8/16/2017 8:03:58 PM EDT

[I initially zeroed my A2 at 3/8 for 300 yards. A couple weeks agi i decided to rezero with a 50 yard zero.
My first zero was within 4 clicks of mechanical zero. The new zero had me running the rear sight damn near all the way to the left.
What changed here? Why would this happen?

Posted: 8/16/2017 8:15:57 PM EDT

[#1]

Quoted:
[I initially zeroed my A2 at 3/8 for 300 yards. A couple weeks agi i decided to rezero with a 50 yard zero.
My first zero was within 4 clicks of mechanical zero. The new zero had me running the rear sight damn near all the way to the left.
What changed here? Why would this happen?

View Quote

is your rear sight elevation bottomed out?

Posted: 8/16/2017 10:31:55 PM EDT

[#2]

http://www.ar15.com/forums/t_3_18/328143_.html
I am using this zero type.

Posted: 8/16/2017 11:25:22 PM EDT

[#3]

There's not that big of a difference between the 2 zeros that I could see would make your POI so far, windage wise. Meaning something changed..... Possibly? Ammo? dropped it? Barrel came loose? FSB is loose? Hmmmmm..........

Posted: 8/17/2017 7:18:22 AM EDT

[#4]

Attached File

Posted: 8/17/2017 10:49:38 AM EDT

[#5]

Quote History

Quoted:
http://www.ar15.com/forums/t_3_18/328143_.html
I am using this zero type.

View Quote

Just say you are using RBIZ. Everyone knows what it is...or should.

I'd start from scratch on the rbiz. You probably screwed up that adjustment...

Posted: 8/17/2017 4:40:00 PM EDT

[#6]

Was my experience in the Army that keeping zero was hit or miss.

Posted: 8/20/2017 1:58:13 AM EDT

[#7]

For a 20" A2, I don't see how the RBIZ is any better than how we did things in the Corps.
The rear sights were 8/3 -2 (3 down bottomed out). Initial zero was shot at 25yds for group, rear sight set at 8/3, and then verified at the 300yd line.
Then 8/3-2 with the small aperture was your 200yd setting. For under 200, and in low light, you use the large aperture.

I assume that the army uses 8/3 as their base and use the large aperture for under 300

Posted: 8/20/2017 9:53:33 AM EDT

[#8]

Quote History

Quoted:
For a 20" A2, I don't see how the RBIZ is any better than how we did things in the Corps.
The rear sights were 8/3 -2 (3 down bottomed out). Initial zero was shot at 25yds for group, rear sight set at 8/3, and then verified at the 300yd line.
Then 8/3-2 with the small aperture was your 200yd setting. For under 200, and in low light, you use the large aperture.

I assume that the army uses 8/3 as their base and use the large aperture for under 300

View Quote

the RBIZ is so you can have a 100 yard zero.

Posted: 8/22/2017 1:04:39 PM EDT

[#9]

So if I sight in my A2 using RIBZ, the 300 through 800 yd settings on the elevation drum will remain intact, ie: 5 = 500yds, correct?

Posted: 8/22/2017 1:42:50 PM EDT

[#10]

I'm not sure it's that simple. It depends on ammo. It is designed for that to be true with M855, but even then I'm not completely sure it comes out exactly like it should. I've never tried. Some people may have though.

Posted: 8/22/2017 2:14:56 PM EDT

[#11]

I'm trying to decide what I want to go with, RIBZ or the 8/3-2 at 25 yd zero like we did in the Marines. I know with the USMC zero, the elevation on the rear drum will be on from 200 on out. It'd be great to be able to use RIBZ with a 100 yd zero and have all the other elevations close vs. holding under at 100 with a 25 yd zero. I don't ask for much...lol.

Posted: 8/22/2017 9:22:21 PM EDT

[#12]

Quote History

Quoted:
For a 20" A2, I don't see how the RBIZ is any better than how we did things in the Corps.
The rear sights were 8/3 -2 (3 down bottomed out). Initial zero was shot at 25yds for group, rear sight set at 8/3, and then verified at the 300yd line.
Then 8/3-2 with the small aperture was your 200yd setting. For under 200, and in low light, you use the large aperture.

I assume that the army uses 8/3 as their base and use the large aperture for under 300

View Quote

Actually BZO for the Corps was with the M855 trajectory, it was shot at 36 yards representing 300 yards. The rear sight should be at 8/3 with small aperture and all elevation adjustments made with the front sight. When you fine tune your zero it should be on at 200 with 8/3-2 and about 1.5" high with 8/3-2 at 100 yds all using the small aperture.

Old Marine

Posted: 8/22/2017 10:13:11 PM EDT

[#13]

Quote History

Quoted:

Actually BZO for the Corps was with the M855 trajectory, it was shot at 36 yards representing 300 yards. The rear sight should be at 8/3 with small aperture and all elevation adjustments made with the front sight. When you fine tune your zero it should be on at 200 with 8/3-2 and about 1.5" high with 8/3-2 at 100 yds all using the small aperture.

Old Marine

View Quote

Thanks SSgt 82-02, I couldn't remember what it was exactly, I looked in my old Battle Skills Training/Essential Subjects Handbook and what it had in there was a 25 yard zero procedure using M855, where you flush the front sight post, mechanically zero the windage, bottom out the rear sight at 8/3-3, then set the rear elevation at 8/3+1, fire a group of 3 shots, and adjust the elevation with the front sight.

So many different sighting schemes and variations makes it hard to decide, but I'm leaning towards the 36 yard zero, I can live a 1-1/2" high at 100yds, plus I want my elevation to be on with the rear drum at farther ranges.

[ARCHIVED THREAD] - A2 zero

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