BUIS. How far off center

I just dialed in a new upper and the BUIS is about 1/3rd of the way between center and left. The FSB does not look canted although I haven't looked really hard yet. If it is, it is not very obvious. It does not affect function, but what are your experiences? I also have not yet tried any other BUIS. I'm going to throw my Eotech on it tomorrow and see if it jives w/ the irons. FWIW it is free floated with a DD Omega..Magpul BUIS gen2.

Don't sweat it too much. Perfectly normal and not really uncommon. You would be surprised how much it might change by switching brands of ammo. And I have mentioned it in another thread previous this one,..don't worry too much if your EOTech doesn't match up perfectly either. You can "lollipop" it to get close then fine tune the actual zero. Sometimes moving your head position won't be noticeable until you go to second guessing your zero. Just remember, zeroed is zeroed. Zero both your irons and your EOTech and don't sweat it if they don't line up perfectly. As long as your shots go where you send them is the only thing that counts. Best of luck,––-foursixty.

Thanks. I have good eyesight, but have a weird undiagnosed vision problem that gives me fits with iron sights and magnified optics, so I don't have too much faith in my iron sight zero anyway. However, the gun that my Eotech is on right now is perfectly cowitnessed with the irons and they are right in the middle.

A lot of times that happens and I think it's a good thing. I am a bit OCD myself and little things like sights not being perfectly centered admittedly bug the crap out of me. I just didn't want you to stress over it, or get worked up thinking something was wrong. I have one rifle that zeroed similar to what you describe yours doing and another pretty identical rifle that actually needed the same amount of windage....the opposite way. Go figure.

I fully understand the vision thing. Started wearing glasses in the fifth grade and when I was in the seventh grade I started wearing contacts. I am almost 30 now and last time I asked the doc just how bad was my vision really? My night vision started giving me fits several years ago with "halo's" around lighting and such. The doc said I have really bad astigmatism and rather than perfect vision of 20/20, mine is actually closer to 20/450.... And....I hate carrots

My MATECH was uncomfortably over to the left initially, but when I loosened and moved it all the way to the rear in the slot, it's almost perfectly centered when zeroed.
Try to play with the front / rear position, should only move 2-3mm but worked for me.

I did not think of that. I will try it. As poster above stated, I too am a little OCD and it bothers me a bit.

I'm the same way. Play with it, and report back when you can.

Sounds like your front sight is very slightly canted but well within spec. Happens during barrel nut tightening. Normal. I wouldn't sweat it if not extreme.

I think it may be the MBUS Gen2.

I replaced 2 sets of gen1 with gen2. Both rifles had the upper faced for a perfect fit with the barrel extenstion. No FSB on either, just long rails.
Anyway, both required lots of left windage to zero......similar to what you said, about 1/3 over. It is just an observation, as I'm over it now.

Topic Moved

After trying another iron sight with the same results, I see now that the front sight is canted to the left a bit. I can see that the gas tube is not directly lined up with the receiver. It doesn't affect function, but I suppose I would have expected better. Is there an easy way get it straight? I've put a few lowers together, but never an upper.

Hmm, my BUIS setup did the same thing (off to the left), the rail is perfectly straight with the upper in my case (RIS II with KAC Flip Up/Matech Rear). I might have to try moving the rear and see what happens. My groups are good at 25 yards, but having the rear sight over almost half way to the left was odd.

My LMT does the same thing. As far as i can tell, it's from a canted FSB because the problem persists even afetr switching rear BUIS. It still can be zeroed, but is far to the left. It's functional at the moment, but I'm eventually going to just put on a longer rail with lo-pro gas block. That will also stop me burning my hand on the hot FSB.

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