I just got my new BCM 16" M4 upper from G&R today.
Looking down at the front sight, the right side post wing is thicker than the left side. Will this affect my zeroing? I don’t think the actual post is off center, but I thought it was weird one side was bigger than the other.
Cosmetic and totally immaterial.
Just act like the ears aren’t there.
Have a pic?
The ears of the FSB on my LMT 16" upper is that way.Its just a minor machining error that is common and has no effect on anything.
I just recently received the same. The right side ear was about twice the thickness of the left ear. A channel is cut between the ears, to accomodate the hole for the fsp. This channel was cut way off center. 20 years of shooting M16/ARs, and I had never seen anything like this. It may be cosmetic, but it’s hardly common. It also means that the post is off-center. You could, no doubt, still zero it, but I think you’d have a slightly f’d up sight picture. Bravo Co took it back and is swapping out the FSB for me.
I would not be happy with it and would send it back.
Ive seen this issue several times over the years with several brands to include some of the clamp on FSB’s.There are a few recent threads on TOS discussing the same.Common,yeah I’d say so…correct maybe not.
None of the FSB’s Ive had personally that the ears were cut off center had any effect on the location of the front site post,and as an example of my recent LMT I mentioned,had absolutely no effect on sight alignment as the port for the sight post is dead center and the alignment/timing of the FSB is correct on the barrel.One ear is thinner and the slot cut slightly more to that side,and has no affect on my sight picture as I do not focus on the ears of the FSB anyway.
If the port for the sight post in the FSB is drilled off enough to greatly affect windage then yeah I’d consider returning the upper,otherwise a few minutes of angle on the windage knob is not a issue for me and IMHO is common with most builds as the alignment/timing is rarely “hair on a flies ars” perfect anyway.
Nit picking a NM HP rifle is one thing but I no longer do it to the same extent on a rack grade utility weapon like a carbine with standard sights,and particularly one with a detachable folding rear BUIS…
That all said,the two concerns I have with the FSB ear being thin is;(1)if the FSB takes a hard impact on that side,which can happen,it may bend or break easier(2)the thin ear has a rather sharp edge that could cut skin when hit.Pure speculation on that as Ive not seen either happen but is my only concerns and further shoulda,woulda,coulda nit pickin.
Just my two cents worth.
i’ve had a couplefew like this over the years… totally inconsequential.
If it ain’t broke, why fix it? It isn’t going to affect jack. Unless you’re so OCD that you can’t stand scratches on a tool, etc. If you really can’t stand it, I would be willing, out of the goodness of my heart, to allow you to donate it to me. 
Just my two cents.
Oof, while I am certainly never concerned with cosmetics on an AR, I would have to say, if I had my choice between a normal FSB, and the one pictured above, I know which one I would pick. That just looks plain fragile, and for me, WOULD affect sight picture, when using irons. While you don’t actually look at the ears when aiming, you do, without realizing it, tend to center things up, when it comes to aperatures and angles.
Having said that, any and every company will have a defect slip through QC here and there, and I am sure BCM will make it right.
/edit solved.
The “ears” are there to protect the front sight post. That’s it. As long as the FSP is GTG, the “ears” matter not.
Exactamundo! I’m very particular about my sight picture, and that would mess me up. The sight housing ears are a significant part of a rifleman’s sight picture.
Of course… you’re not supposed to use your IRONs anyway right? :rolleyes:
Poor machining…why pay for it?
Should have been caught during QC. I know they are “tools” but it seems like the AR world has come to accept shoddy machine work as acceptable when its not in any other segment in the gun world. I wouldn’t buy a gun that the factory messed up on, and sold anyways. A FSB machined that off center means one of the ears is much more likely to break, and they are supposed to be a certain thickness for a reason. I’d be pretty pissed if my gun slid off a rack or got knocked on something, and that flimsy ear broke off…
nice quality 
and people try to make fun of Oly, that’s horrible!
Gotta agree that it is a QC miss. No matter what, IMO that is a mistake and if you are not pleased with it, ask to have it corrected. It is your hard earned money after all. I am not necessarily an OC / picky person type, but a FSP like the one posted in the pic, would piss me off.
edit - I would like to add that sometimes things slip through the cracks. Sucks but it does happen. I would not necessarily dong a company for an issue, unless if issues were the norm for a company, but rather how it is handled afterward.
The difference is Oly will do jack shit to make it right, if you don’t like something from BCM, they at least try to make you happy. OP, if this really gets your knickers in a twist, take it up with Bravo.
100% Normal. See this with everything from Colt to LMT. It does not affect a single thing.
C4
What you have to understand is that AR’s follow the TDP spec. This means that if there is not a specification on this (thickness of the ear) then there is NO standard for it. So, one wing can be thinner than another and that would pass a .Gov inspection.
I will have to check, but I bet there is no specs for the thickness. If there is, I bet it is a +/- thing and something that “looks” incorrect, would actually be within the spec.
C4