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Thread: First Look at BCM's NEW M4 Upper Receiver

  1. #161
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    Last weekend I got a chance to shoot an upper I swapped one of these new receivers onto and I wanted to point out an observation I made. I had a Troy buis (BCM branded) and an Aimpoint PRO on the old upper and I moved them over to the new one to re-zero. The buis was previously zeroed about 6 clicks left of center. On the new upper the buis zeroed 4 clicks right of center. The PRO needed about 15 clicks in elevation to shift the group down and on target but no windage adjustment was needed. The optic adjustment sounds like a lot but I have no idea how far from mechanical zero it was when it was zeroed on the old upper. It may be closer to mechanical zero now than it was before.

    I knew I'd have to re-zero but for some reason I never thought about how much uppers can vary. I'm pointing this out for the benefit of consideration the next time someone posts an issue with a canted fsb, weapon that won't zero, maxed out windage/elevation etc. In my mind it's easy to jump to the conclusion of the fsb being canted in those situations but it's obvious to me now that sight/zeroing issues can be attributed to other parts; most likely a combination of parts adding up to a problem. It's good to know BCM has taken the effort to produce dimensionally correct uppers when there are so many poorly made ones floating around.
    Last edited by Eric D.; 02-26-14 at 19:55.
    B.A.S. Mechanical Engineering Technology

  2. #162
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    Quote Originally Posted by cjb View Post
    Sorry you dont find my informative post enlighting. Just callin' em as I see em.
    I thought it was informative and contributes to the thread about the product. Thanks.

  3. #163
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    Received my BCM upper from Grant three days ago (nice fast shipping). Looking the upper over I was impressed with the machining and the quality of the anodizing. The color is slightly grey (which I like) close to the Mega forged lower I had for this build. This build is or was a spare parts build until I decided to try the new BCM upper as part of it.

    I had an couple unused barrels and decided to use the Rainier Arms Select Medcon 16" with ION Bond finish I had in a box. The fit was VERY tight (Yes!) and I had to use a heat gun to warm the upper enough to slide the barrel in.

    Once the upper had cooled I put some Aeroshell 33ms on the upper threads and BCM barrel nut. Torqued to 45 Ft.Lbs. the standard barrel nut indexed perfectly. The feed ramps lined up perfectly, and I mean perfectly. I tapped in the Vltor pinned & screwed gas block installed the gas tube and boom everything aligned perfectly.

    I have a Fortis Rev 14" that I bought on a whim some time ago. The Rev is an interesting, light weight, inexpensive and well made rail that works with a standard barrel nut. It installed in just a few minutes.

    I have a spare BCM BCG and a Generic BCG marked MPI which I went over and replaced the ejector, ejector spring, extractor spring, Etc. I checked head space of the Generic BCG bolt and I think I'll use it for awhile to see how it holds up while keeping the BCM BCG for a spare. (I use BCM or Noveske BCGs in all other rifles)

    I'm going to laser bore sight the irons tonight so I can take it out soon as I can get away. I'll see what it'll do with some decent ammo compared to my BCM SS upper.

    I am very impressed with this new BCM upper.
    If you like a tight hole the BCM might be for you.
    Last edited by ScottsBad; 03-01-14 at 17:47.

  4. #164
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    Quote Originally Posted by Irish View Post
    I thought it was informative and contributes to the thread about the product. Thanks.
    Regarding cjb's post: Me too.

  5. #165
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    Aw shoot, I thought I was about done building these things, come on tax refund.

  6. #166
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    Not sure why everyone seems to be focused on cjb's post so I guess I will clarify. If you look specifically at the part that I highlighted I made mention that those items which he pointed out have ZERO impact on the overall function of the weapon.

    In addition with very few exceptions, no one is hand fitting uppers to lowers and it was never designed to be that way. Uppers and lowers are produced to a spec with certain tolerances that are allowed.

    As for him being banned it was two fold. One he requested that his profile being deleted (which we don't do) and then he decided to go over to another website and make posts about M4C to their peanut gallery.

    So now that we have that cleared let's get back on track to this topic.



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  7. #167
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    I ordered a standard M4 upper from BCM right before they started selling the BCM4. After reading through the thread I'm torn between keeping the one I have and exchanging it for the BCM4. I don't have the correct tools to measure the specs on the upper I have.

    Any thoughts?
    0311
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  8. #168
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    Cool

    Quote Originally Posted by Dist. Expert 26 View Post
    I ordered a standard M4 upper from BCM right before they started selling the BCM4. After reading through the thread I'm torn between keeping the one I have and exchanging it for the BCM4. I don't have the correct tools to measure the specs on the upper I have.
    Any thoughts?
    Grant said:
    Quote Originally Posted by C4IGrant View Post
    ...BCM has had to reject upwards of 50% of the upper receivers they get in because they did not meet their specs and standards...
    I take that to mean the rest met "their specs and standards" which would include yours (and the ones I have). From what I understand from the rest of Grant's OP is that BCM has taken steps to assure that a much higher percentage of the uppers they receive meet those "specs and standards" not that ours do not or that they changed those "specs and standards".
    If I am wrong about this I am sure someone will correct me.

    Bill Tidler Jr.
    **************

    ...We have long maintained that the only accessories that a 1911 needs are a trigger you can manage, sights that you can see, and a dehorning job. That still goes.
    ~Jeff Cooper

  9. #169
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    Quote Originally Posted by Dist. Expert 26 View Post
    I ordered a standard M4 upper from BCM right before they started selling the BCM4. After reading through the thread I'm torn between keeping the one I have and exchanging it for the BCM4. I don't have the correct tools to measure the specs on the upper I have.

    Any thoughts?
    I got one of their older upper receivers and built it up about a week or two before this thread started and I'm very happy with it. I think if you keep it you wont be disappointed.

  10. #170
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    I must have missed the harps playing and angels singing when I opened the box on mine. I don't think it did a backflip, either.

    All that I noticed is the same quality that I have ever received from BCM. I slid a BCM CH and BCG in it and slapped it on a BCM lower. Pretty much, boringly GTG as far as fit and finish. I don't expect anything different when I get to shoot it. It is just an upper that's perfectly finished and in spec. They didn't reinvent the wheel....just made sure that it's round and will fit on your wagon.

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