Is this a crack?

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  • tommy gunn

    Active Member
    Apr 7, 2012
    813
    calvert county
    I was cleaning my plr-16 today and I saw what kinda looks like a crack in the bolt. Is it a crack or a gouge? Should I be worried?
    uploadfromtaptalk1437841233973.jpg
     

    jpk1md

    Ultimate Member
    Jan 13, 2007
    11,313
    Is that cast or machined?

    As I look at the part of the pic it appears to have been machined as part of the manufacturing process due to what appear to be machine marks that create the circular rings around the part

    Whats not evident in the pic is whether the material in question flares out OR does it look llke it was gouged out of the surface
     

    tommy gunn

    Active Member
    Apr 7, 2012
    813
    calvert county
    Thanks guys. I was just worried cause I never noticed it before. Had to break out the magnifying glass just to really see it. I try to inspect every part when I'm cleaning for anything I may find.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    Thanks guys. I was just worried cause I never noticed it before. Had to break out the magnifying glass just to really see it. I try to inspect every part when I'm cleaning for anything I may find.

    You are doing it right.


    Thats the important part about cleaning, you mainly do it to inspect. Otherwise just add oil and shoot.
     

    Blacksmith101

    Grumpy Old Man
    Jun 22, 2012
    22,156
    From the picture that looks to me like a forging defect, possibly a lap or failure to fill, rather than a casting problem and probably won't result in a catastrophic failure. Check it when you are cleaning to be sure it doesn't get bigger.

    If you want to be sure it isn't a crack you could check it with Liquid Penetrant Inspection however analyzing the results of dye checking does require some judgement and some skill is involved in accurately preforming the test. It is the least expensive non destructive testing method and will work with defects that connect to the surface of a part. Other related methods such as Florescent Penetrant (Zyglo) or Magnetic Particle (Magnaflux) require expensive equipment.

    Liquid Penetrant test kits are not exactly cheap and I don't know a source of the materials in small quantities but here is a reasonable price kit and a thorough search may find better deals.
    https://www.pegasusautoracing.com/productdetails.asp?RecID=1207

    Here is a writeup of how it is done which includes basic interpretation of results:
    http://www.callingtonhaven.com/_assets/non_destructive_testing/manual_visible_dye_penetrant.pdf

    The process is reliable enough that I have grounded B-52 and other aircraft based on the results. However when we inspected all the bolts on the M-1 Carbines on base we used MagnaGlow florescent magnetic particle inspection but the government has lots of your money to buy equipment.
     

    tommy gunn

    Active Member
    Apr 7, 2012
    813
    calvert county
    I learned another interesting thing about my plr 16 this weekend. It don't like steel case ammo. The extractor kept ripping the rim off of the shell. Thankfully I had my traveling cleaning kit with me so I could knock the shell out with the cleaning rod. Massive pain in the butt.
     

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