Upper receiver marks

Discussion in 'AR-15 Discussion' started by EW1066, Jul 14, 2010.

  1. EW1066

    EW1066 Member Supporter

    344
    0
    16
    This may seem silly to some but my curiosity is killing me. On the left side of all cast and forged uppers ( that I have seen )there is an embossment that coincides with the recess were the cam pin is when the BCG is closed. On that embossment on the outside of the receiver there is a .250 vertical line. Does anyone know the purpose or meaning of this line. I cant seem to find an answer with the search function. And like I said its just bugging the dog crap out of me. Everything else on this gun has function and meaning....except this little line. I'm getting close to losing sleep on this one. I sometimes will fixate and obsess over something like this. Right now it's just fixation. Please help me !

    Thanks in advance.

    Vince
     
  2. EW1066

    EW1066 Member Supporter

    344
    0
    16
    Would I be correct in assuming that no one here knows either? Well, I guess I don't feel so bad. It's still gonna bug me though.

    I'm still open to an answer if anyone has one.


    Vince
     

  3. willfully armed

    willfully armed New Member

    2,096
    1
    0
    give up a pic man!


    One second thought, its likely a reference point for an optic.
     
    Last edited: Jul 15, 2010
  4. EW1066

    EW1066 Member Supporter

    344
    0
    16
    [​IMG]

    Okay maybe this will help.

    Vince
     
  5. Jpyle

    Jpyle New Member

    4,828
    0
    0
    With no first hand knowledge my guess would be that it is a registration mark to establish a zero point for all future measurements during the machining process similar to those found on multi-color print work.