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Thread: NSR 13.5 rail and BCM 16" upper. Something is crooked.

  1. #11
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    Quote Originally Posted by Failure2Stop View Post
    I wrote about this a while ago.

    Basically, the culprit is most likely your barrel extension or upper receiver.

    The dimensions of those areas are not required by spec to be at the level of straightness that you need to ensure that your barrel will be perfectly centered inside a floating tube.

    Still, it is not a functional issue, and if you can't get over it you can fix it with some work.


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    Quote Originally Posted by 1911-A1 View Post
    Is this where those receiver truing tools come in?
    That's what I was thinking.

    This issue has been reported twice this week with new builds.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
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  2. #12
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    Has BCM been replacing the barrels in question, or are they saying "If the gun works, we're not replacing anything."?

  3. #13
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    We'll see. Mine arrived there yesterday--waiting for a response/call or it to get shipped back. ::fingers crossed it gets fixed, not just realigned/shimmed::

  4. #14
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    Quote Originally Posted by evi1joe View Post
    We'll see. Mine arrived there yesterday--waiting for a response/call or it to get shipped back. ::fingers crossed it gets fixed, not just realigned/shimmed::
    How much was yours off by?

  5. #15
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    The 12" C4 rails were probably just 3/16"...maybe even 1/4" closer to the barrel on the left and 1/4" further on the other side--it was definitely visible, but when I held it in place and tightened it down, I could get it to where it was barely visibly noticeable--sticking my two forefingers, one would go in a bit, the other wouldn't (so it was still off).
    I have a feeling it might shoot itself out of alignment unless I used red loctite and/or a shim.

    NOTE: The VTAC ALPHA 13"s were off even more...I wish I'd measured, but I'd say there was 33-40% more space between the barrel and the rail on one side.

    I actually plan on running the VTAC until Fortis or someone comes out with a lightweight keymod that uses a standard barrel nut. I've now heard of 3 people with the same issue. Hopefully we'll all get it "straightened" out.

  6. #16
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    Quote Originally Posted by 1911-A1 View Post
    Is this where those receiver truing tools come in?
    Sometimes.

    I'm not being intentionally cryptic, it's just that it can be in a few different places, or with a tolerance stack that isn't visible until 10" from the barrel nut.

    If it's the threads, there isn't really anything you can do.
    If it's between the barrel extension and the face of the receiver, they can be "flattened"; the extent of which work can be anything between simple and soul-crushing.

    The big thing to remember is that the TDP doesn't control these dimensions as tightly as needed to have precise alignment of free-floated tubes and barrels; so you can have quality components all around and still have a "misaligned" barrel and tube. Frustrating, I know, but one of the results of advancing a design that was not specifically spec'd for that setup.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  7. #17
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    This is another guy, from TOS, who just put a Troy ALPHA on his BCM blem upper...my VTAC ALPHA was off exactly like this:

    Last edited by evi1joe; 08-20-13 at 17:54.

  8. #18
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    The problem there is mounting BUIS on the rig. You may or may not be able to adjust windage enough to even get it on paper. I had the same issue with a TRX Extreme on an unnamed upper. I was able to true that setup through judicious sanding of the interface and bridging the upper & forend top rail while torquing everything down.

    And yes it was a pain in the ass.

  9. #19
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    Yeah, for a $1200 new (non-blem) complete upper group, I shouldn't have to do all that (in my opinion--we'll see).

    My hope is that they just replace it with a new one that is dead-center aligned.

  10. #20
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    My 4 year old BCM upper had the exact same problem. Regardless of the rail system/barrel nut, it was misaligned. It also had other issues, so I replaced the upper receiver, which took care of it.

    When I originally purchased it from BCM, it also had a slightly canted FSB (to the left, when looking down the rifle while firing).

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