I recently got a Bushmaster A3 upper.  I picked up a GG&G Back-up Iron Sight to sit on the rail behind an EOTech.  The trouble is I'm having to raise the front sight post way up to get it near sighted-in.  As it is, the top of the post is above the protective sides of the base, and it looks wierd.  I can take a picture of it and post it here if this helps.

I don't like the way the front sight looks.  Am I being picky?  I don't go around looking at typical post heights, but on my A2 the bottom part of the sight post sits nice and flush with the hole in the base.  I hardly had to adjust it at all.

I'm not sure what to do about this.  I can't see any way to adjust elevation on the B.U.I.S.  I don't know af any way to "fix" the upper.  I'm not sure what causes this in the first place.  It just seems to me that the rear sight is too high.

Is there something about this sight that I'm missing?

Any suggestions?

First of all, why are you messing with your irons if they are sighted in, they have nothing to do with your optic. Iron sights are zeroed independently to a given point of aim, and the optic is zeroed to the same place, but also independently. Take the optic off and re-zero your iron sights, then leave it alone! When you put your optic on to zero it, don't even think about the irons, just zero to the same target. If the irons are not usable thru the optic, your can't just move them so you can, as all you then have accomplished is to ruin the zero of the irons which are supposed to be your back up if the batteries in the optic fail. If the optic is too high like the Eotechs are, then don't plan on having a co-witness or go get an Aimpoint or Trijicon reflex or tri-power optic that all do allow a co-witness as they are lower in position of the lens. You can't mix zeroing optics and irons, they are dif. animals.
Good shootin, Jack

Sorry I miss-undertstood your problem and wasted so much of your time by wasting my time to help you out,Go fuck yourself!
Jack

Here's what I'm talking about:

Jack (3rdtk):  I apologize, sorry I got so gruff, you were right.  You were trying to help, and I was far too critical.

Have you tried any other rear sight or the carry handle?
Worst case is a machining error on the barrel or upper.
Does GG&G make a rear MAD for the AR10? shorter-longer.

Blkbrd, I don't have another rear sight, but I do have access to a carry handle.  I'll give it a try.

I'm not sure what you're asking on the last question.  Are you suggesting I try the MAD for an AR10?  I'm confused.

Do you think I'm making a big deal over nothing?  Does the post look too high to you?

Carbine_Man
I think we were both wrong, I took a close look at my 2 Bushy M4s one with a Knights 600m and one with a GG&G MAD and they both look just like yours, the pins stick up over the ears about .030", Bushmaster uses SMALL protective ears, I looked at my Armalites with an A2 and a GG&G MAD and the pin sits lower in the hole plus the Armalite uses ears that are about twice the size of the bushmaster ears.
About the AR10 I was speculating that you may have an AR10 rear sight that was a differant hight, I was wrong. Bushmaster just uses tiny protective ears, never noticed till now.
I wonder if this is why my Armalites sights seem clearer?
I don't think its worth messing with the carry handle as I only have 2MOA differance in rear sight settings between my carry handle and MAD on my Bushmaster.
however I do sight in with the carry handle and then with flipups and write down the differance just in case I need to switch, I still trust carry handle A2 sights more than scopes with flip up backup sights.

Ahhh, the old sight height issue rears its ugly head again.

I'm guessing the GGG BUIS may be set up for a Colt upper receiver & front sight. Colt and Bushy use different measurements - so much so that Bushy warns about using a Colt detach carry handle on a Bushy rifle (or vice versa).

Check out the Bushmaster website's FAQ area; it's around there somewhere.

Call GG&G and ask them about applications. Maybe they have some variations.

I (and others) have a similar problem when mating a genuine new Colt M4 barrel assy onto a surplus Colt late 1960s A1 upper: even to get an approximate 'guesstimate on the sofa' zero, my FS has to be cranked up 'way high' - worse than yours!

Bill Wiese
San Jose, CA

I think bwiese hit the mark!  Can you confirm if your upper is a factory assembled Bushmaster upper or a "Parts" upper that may include a Colt barrel or Upper receiver?

I have been told by people that should know, that the AR-15 and AR-10 rear back up sights are the same height!  Accordingly, I do not beleave the problem can be that you have an AR-10 GG&G site on an AR-15... (Note that I have never had both to compare at the same time so I could be wrong!)

After to try to confirm if you upper is a factory upper, I would call GG&G and ask them what is up!  This sounds EXACTLY like the carry handle issue that Bushmaster used to discuss on their FAQ page so I will guess that you have a Colt receiver with a bushmaster barrel?  BUT I'VE BEEN KNOWN TO BE WRONG twice a day and I am over due!

Good Luck & Please let us know if you figure it out!

Checked 3 different Bushmaster assembled M4s with flip up sights. Knights 600m, GG&G MAD and ARMS #40, The front sight posts all look like yours.
Have the ears shrunk on Bushmaster front sights?

Well, the plot thickens.

I bought this upper (no b/bc/ch) at a gun show for $395, no tax.  I went up to a dealer, and asked him if he sold Bushmaster uppers.  He said "no" just as I looked down and noticed one that had Bushmaster written on the price tag.  I said "what about this?"  He quickly mumbled, "oh yeah, I forgot about that one" or something like that.  So now I'm suspicious.

The barrel assembly is definitely a Bushy (its got the "B MP" on the barrel, and the shape and finish is identical to my old barrel.)  However, I compared my upper to a complete new rifle with the A3 upper.  On mine, there is an "A" on the upper receiver just above the forward assist.  The Bushy doesn't have that.  Also, mine has a very shallow groove running along the side under the rail.  There were other small differences as well,but they are very small diferences as far as I can see.

The lockup with the new A3 upper and the lower is the same as my old A2 upper.

Are all Bushy upper receivers "identical?"  Do any of them have the "A" on the upper?  Did the dealer take a Bushy barrel assembly and put it on a generic upper receiver?  Can I know this for sure?

I have to say, there's nothing "wrong" with the upper.  It shoots fine, and the quality of the finish is fine.  My Army son was the guy sighting in the irons, and he said he didn't think the post was high enough after he'd raised it as you see in the picture.  I can turn on the EOTech and the center dot goes right on the post when using the irons.  I can't confirm that the post is the right height now or not, I'm just mostly going by my son's comments.

I have loc-tite on the GG&G BUIS, so I'm reluctant to pull it off just to try the carry handle.

I looked around the Bushmaster site and didn't find anything in the FAQ's.

I can't do any more sighting-in for a while, because I lost my place to shoot.  So I guess the mystery will remain unresolved for now.  In any case, I'm not sure what I can do about it, short of selling the upper and buying another, which would be dumb.

I will give GG&G a call though.  I'l let you know what happens, and I appreciate any other comments you may have.

Called GG&G, they said this problem rarely happens.  Couldn't offer anything as a fix other than trying different ammo. They suggested that I keep messing with it and that if its still a problem, they would have a look at it and tell me if the dimensions are accurate.  Maybe this winter?