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Thread: Is this in spec for an upper

  1. #11
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    I'll check mine when I get home, but I'd say shoot it. I can't see it giving you any issues.

  2. #12
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    Quote Originally Posted by redmist View Post
    Since it's a forging, all the "Specs" are internal for the most part. As long as the charging handle latch cut is done correctly I see no issue other than cosmetic.

    We have seen forgings with core shift as far as .030 out. We have also seen them with extreme taper from one end to the other.

    Ryan
    The forging drawing states a maximum mismatch of 0.020"....

  3. #13
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    Here ya go... I posted this around 2013???


    It has some technical info as far as what is seen when machining forgings.

    So when you order forgings, they come in large boxes, stacked in layers. Typically you see 400 pieces per large box.





    Each forging has a "Die Mark" "Strike Mark" whatever you want to call it on the part itself, typically this is on the port door area of the forging. This is why you don't see it after process as that area is removed in machining.





    Here are examples of what we see as far as blems, or quality issues with the forgings. In this first example, the forging has what I would describe as ripples along with a decent indentation half way down the rail area of the forging. This would be a perfectly functional part, however I would expect someone to question quality based on this. This could also affect fixtureing depending on how a company is holding the forging. In the end, it's a scrap part from a QC standpoint.






    Another MAJOR problem is "Shift" this has been a huge issue in some cases, as we have seen it as far out as .030 in some cases. The two halves that come together to make the strike do not line up, and you end up with one side of the part, higher or lower than the other side. In this example, you can see the center line, and the two halves on both sides shifted top to bottom. One being higher than the other.






    In this example we have a massive indentation in the forging. I am almost wanting to run this forging just to see how thin the wall will be after cutting! Either way, this is a junk forging.





    Another view of same forging:






    All of this is compounded by the fact that these also move during the cutting operation. It can be predicted yes, but each die has it's own characteristic. Probing can line you up on the forging, however compensating for movement in the part itself is a trial and error process, and it changes with each die. If done correctly you end up with a nice part!! But if you start with crap, you end up with crap. right now the forgings are crap. Those steps that you see just below the rail on your upper receiver???? I have examples here that have so much taper in the forging that the step actually fades to a perfect flat on both sides. Sometimes the step is more prominent on one side than the other. Again, this can be tracked right down to the die.


    Good part.

    Founder and co-owner/operator at 2A-Armament

  4. #14
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    Just checked a few of mine and did not observe a similar issue.

    A forged NEA on the left and an Aero Precision on the right.



    A billet MI on the left and a Billet NEA on the right.

  5. #15
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    Just checked my sample of two.

    Palmetto
    L=.118"
    R=.108"

    BCM4
    L=.116"
    R=.120"

    Clarence
    Lija 4 groove AR24 1:8 twist
    BCM4 upper and BCG
    Anderson lower
    Geissele Hi-Speed National Match - Match Rifle trigger
    Leupold MK AR 6-18x40mm

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