I just got home today to my new BCM upper, took it out of the box, wiped all the oil off, put my rails on it, and went to put it on the lower. The front pin went in just fine, but the rear pin WILL NOT go through. More specifically, I don’t believe it can go through because the upper will not go as far down into the lower like it should. I’m no expert to the AR platform, but am also no idiot either, and from what it looks like, the piece that sits down in the lower and has the pin go through it (no idea what that’s called) is slightly - as in a millimeter maybe - too long and the whole thing won’t fit perfectly flush or let me put the pin through. Is there a way to fix this??? Or will it just need to go back to BravoCompany? And I even took the BCG and charging handle out to make sure there was not issue with either of those. Maybe I’m missing something but I don’t think I am. I’ll be really bummed if it has to go back; I was looking forward to breaking it in for my spring break. :mad:
Did you try pushing down harder? Is there anything you can see that is binding? Sometimes it can be a tight fit for brand new parts.
Contact Bravo and allow them to fix it…wont take em long.
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Did you buy or build the lower? Your buffer tube prohibiting it?
Nevermind, saw that you checked the BCG.
Is there a possibility it is the lower and not the upper? Can you try a different lower?
Can you post some pics?
I bought the lower from Grant about three months ago. It was a blem lower, but I know that’s not it because I fitted the uppers from my dad’s two ARs on it and they fit fine.
I tried pushing pretty hard. The front pin didn’t want to go at first but then it went after a few tries, so I figured the same would happen with the rear…not so. So I tried a few more times…and a few more times…
Then I tried to put it on one of my dad’s lowers and still the same thing. So I’m 99.99% sure it’s the upper itself. And I don’t believe it’s got anything to do with the buffer tube. I can hold it up to the light and see a microscopic gap between the lower and upper running from about the bolt release to the top of the lower and end of the upper (where it curves). It doesn’t appear that the upper is even touching anywhere near the buffer tube.
Has anyone heard of this happening before? Does the piece that connects the upper to the lower ever get made too long so it won’t fit? Or am I the first?
should have got a delton :haha:
I would say try a different lower or put the upper onto a different lower (not your new BCM) and see what happens. Pictures would be helpful.
I’ve already done that and it still wouldn’t go so it’s not the lower; other uppers fit fine on it. And I don’t have a camera, so I can’t post pics. 
One of my BCM uppers fits very snug onto my LMT lower. I have to play with it a bit but it goes on. Contact BCM as Wahoo stated above and let them take care of it. They have excellent customer service.
How is the best way to get in touch with them? I’ve called about a dozen times in the last 30-45 minutes and can’t get through. Is e-mail better?
I had an issue like this before. It seemed the shelf on the lower, right behind the trigger and below the rear take down pin was higher than on a different lower I had. Wouldn’t let me close the upper. My BCM upper works great with it though.
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e-mail.
I would try a different take down pin if you have one. My SR-15 lower wouldn’t fit on some uppers until I changed the pins.
It seems like I’m having the same problem, only the other way around…
To the OP, no, upper/lower fitment issues are not a new question; it comes up from time to time, however…
This is from the “Rules” button at the top of the page, with particular emphasis on #4:
https://www.m4carbine.net/faq.php?faq=vb_faq#faq_new_faq_item
If you end up with photos and want to post them, let me know and they’ll be added to the thread.
Otherwise, contact the vendor/manufacturer, as you agreed to do by the act of registering to and signing on to this forum, by voice and electronic means, and give them a reasonable chance to respond…hint – like, a week. Don’t mimic the poor, benighted idiot that posted a thread about PSA that pissed and moaned that they didn’t get back to him within 48 hours…during SHOT Show week :rolleyes: :haha:
If they do not roger up, we’ll open 'er up again, so you can describe the lack of resolution.
If they do roger up, we’ll STILL open 'er up again so that you can describe the resolution OR lack thereof.
Please keep me, or IG, or another of the mods appraised via PM.
We have progress. Re-opened.
Some folks need to bear in mind that there’s a difference between posting to say something, and posting because you have something to say.
There’s a big difference between the two, with the latter being the preference.