Zeroing Red Dot And BUIS Question

[Scrod314]

Hello... I zeroed my red dot last weekend, then zeroed my iron sights yesterday. I noticed last night if I have my iron sights up and the red dot on to absolute co-witness, the rear sight covers up part of the red dot. The only way to fix this is to adjust the windage on my rear sight way left. Did I do something wrong? My other AR doesn't have this issue, if it is even an issue. Thanks for any help.

 

[DMW1116]

Not sure I follow. Can you take a picture of the issue?

 

[Scrod314]

I sighted in the gold dot and BUIS separately. Both zeroed, but when I absolute co-witness, gold dot and BUIS don't line up? Shouldn't the dot be sittingon top of the front sight post of my buis?

 

[DMW1116]

In theory yes but that’s pretty close. How far is the zero distance? My eyes would likely cause a shift just the way I look at sights sometimes. Do both hit where you want when used independently?

 

[DMW1116]

Your post and dot both seem a bit to the right. Is that just me or do you see that in use? Is that the small or large peep aperture?

 

[Scrod314]

It's the large peep. I might just be crazy. Screw it. Gives me a reason to go back to the range today to look at it again.

 

[DMW1116]

Is the rear sight an L-Shape where one leg has the small peep and another has the big peep or is it like the Magpul MBUS sights where the small peep folds into the large one?

The L-Shaped ones sometimes move a little when you change. The MBUS style seem like they’d do so less. I generally zero with the small peep but I also shoot at 100 yards or more with my M16 A4gery for load testing, so I rarely use the large one.

 

[Scrod314]

MBUS Pro. It has a small peep that folds down to a large peep.

 

[DMW1116]

Generally I’d recommend zeroing with the small peep. If you didn’t that might line things up a bit more, but I don’t think it’s a problem unless one hits and the other doesn’t.

 

[marvin02]

Can you zero the dot for POA=POI and then zero the sight for a 6 o'clock hold? That should put the dot right on top of your front post when it's on.

 

[trackskippy]

The dot on mine is split in half by the front post when I sight with the irons, sorta like yours. The dot doesnt sit on top of the post.

I have the irons zeroed to POA-POI, not a 6 o'clock hold with a specific offset.

 

[browneu]

View attachment 1104947 I sighted in the gold dot and BUIS separately. Both zeroed, but when I absolute co-witness, gold dot and BUIS don't line up? Shouldn't the dot be sittingon top of the front sight post of my buis?

What red dot is that? I like the amber reticle.

 

[Chuck R.]

View attachment 1104947 I sighted in the gold dot and BUIS separately. Both zeroed, but when I absolute co-witness, gold dot and BUIS don't line up? Shouldn't the dot be sittingon top of the front sight post of my buis?

Mine never perfectly align either and yours are close.

Method I learned (Army) is to:

1. Zero irons 1st,
2. Then co-witness the RDS to the irons
3. Confirm the zero of the RDS

In theory, the RDS should be GTG after being co-witnessed while sitting on the post, but I always have to make a small adjustment.

 

[Scrod314]

My sight is an HE512C-GD. So, I found my handguard to be slightly canted. It was an easy fix. Everything lines up perfect now.
Only problem is I wasted $50 in ammo trying to figure out the issue. I bought the upper as complete. Kind of irritating.

 

[DMW1116]

That is the only gripe I have with my MBUS on my DMR (discount marksman rifle). Putting pressure on the hand guard can move the sights and an off-line hand guard will throw the front sight off. I’ve shot them out to 200 yards with good hits on silhouette targets so I may be making more out of it than it really deserves.