AR-15 Bolt Carrier Discoloration

Discussion in 'AR-15 Discussion' started by thatguy510, Feb 2, 2013.

  1. thatguy510

    thatguy510 New Member

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    You guys usually have insight into everything. So, I thought I'd come here looking for an answer. Both BCGs are from the same model ar. The bottom one is significantly lighter than the other. The top has never been fired out of the factory and the lower has a 100 rounds through it? What's up with te difference in color? Just different runs in manufacturing?any possible issues in the future (ie rust or corrosion)? Already sent a pic to the manufacturer but wanted to hear all your opinions first.
     

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  2. Quentin

    Quentin New Member

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    Which model AR? Some brands are very picky about their parts suppliers and others buy the deal of the week, which could explain the difference.
     

  3. thatguy510

    thatguy510 New Member

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    Sig Sauer.
     
    Last edited: Feb 2, 2013
  4. purehavoc

    purehavoc New Member

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    Looks to me like a piss poor parkerization job ,There are 2 reasons the color change happens . #1 Too low of heat during the process causes a lighter color in the Park or, #2 it didnt get oiled immediately after the process , neither will hurt anything and wont cause problems later its just a cosmetic flaw and I would guess its due to #1
     
  5. sweeper22

    sweeper22 New Member

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    By the looks of them the lower (lighter colored) carrier also appears to be the lighter weight/lighter duty/cheaper of the two as well. That's just my own take based on one photo.

    But both will probably serve you just fine. And if you're concerned about quality, you could always track down an M16 BCG ($125-200 when you can find them) as an upgrade...and tuck away the light weight as a spare.
     
  6. thatguy510

    thatguy510 New Member

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    Sorry but I have to disagree with that. Not only are they from the same make and model but were bought new within a month of each other. It is more likely a finish issue like purehavoc said than a material issue. Sig is really good about being within spec which is why I was surprised by this in the first place. I am curious though, what in the pic makes you think the materials are different and it isn't just a finish issue? For the life of me, I can see a thing. If they were the same color, they'd be almost identical all the way down to the staking.
     
    Last edited: Feb 2, 2013
  7. purehavoc

    purehavoc New Member

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    I wouldnt worry about it honestly , when the park process is below 170 degrees it creates that light color , you can also do it cold and it creates a white to light grey color thats really kind of neat but not really acceptable color finish for a AR :D
     
  8. sweeper22

    sweeper22 New Member

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    I don't think the materials are different. I see a difference in the structure. Admittedly, this could be a case of the angle of the picture fooling my eyes. But the body of the carrier in the top one appears to be the fuller "AR Enhanced" style, while the lower could be the lighter weight "SP1" type. I'm looking specifically at the lower right portions (in the picture) of each carrier.

    And again, maybe it's just a deceiving angle in the pic.

    Line them up belly to belly, and I suppose you'll have that answered.
     
  9. purehavoc

    purehavoc New Member

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    Hey Sweeper help me out on one of those PSA lower build kits you have on ebay . I need one to finish up a build ,
     
  10. thatguy510

    thatguy510 New Member

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    I see what your saying. If you line the up correctly and not as I did you'd see they are exactly the same. I didn't pay attention to that because my question pertained only to the finish.
     
  11. GeneralPatton

    GeneralPatton New Member

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    Photo angles can make your eyes go ape****. I had a windowed pmag in hand I traded to a buddy for a non-windowed (I'm trying to get employed in his shop, so yes it's sucking up) but holding them next to one another, the non-windowed looks smaller. It's just the angle and your eyes. They can be fooled quite easily by shadows and molding levels. And the parkerization (spelling) on different days from different batch mixes could be the source of color differential. It all depends on who mixed it each time
     
  12. fsted2a

    fsted2a New Member

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    Without having read the rest of the posts, I would have said that the AR MFR was purchasing from two different contractors for their carrier, either due to cost or availability. Agreeing with what another poster said regarding SP1 Vs AR, the differences in the carriers is to prevent the correct operation of a DIAS or lightning link, or at least one of the purposes. I have seen some of the BS excuses put out for it, but that is the one I beleive most.
     
  13. purehavoc

    purehavoc New Member

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    Im going to park some stuff tomorrow , I will post up pics when its done . Wish me luck ;)
     
  14. thatguy510

    thatguy510 New Member

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    One of the rifles has roughly 200 rounds through it and the other hasn't been fired. Can I switch the BCGs around without a problem?
     
  15. fsted2a

    fsted2a New Member

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    I strongly recommend keeping the bolt itself with the same barrel. I don't have any data in front of me to support this, just what I was taught from the Colt M16 repairers course a few years back. If you don't keep the bolt with the same gun, find someone who can check the headspace with your different bolt to make sure it is good to go.
     
  16. purehavoc

    purehavoc New Member

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    So what do you do if your head space is off ? arent ARs pretty much non adjustable ? I have always been told so long as you use a barrel with matching barrel nut of the same manufacturer and a mil spec bolt , No problems .
    Whats your thoughts on that ?
     
  17. robocop10mm

    robocop10mm Lifetime Supporting Member

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    Top one appears to be an M-16 carrier. The different amount of metal at the rear is to trip the auto sear. Adds a small amount of weight that is desireable
     
  18. fsted2a

    fsted2a New Member

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    I suggest replacing the bolt if your guage says no go. Then try again.
     
  19. JonM

    JonM Moderator

    Once it closes on a 223 or 556 (whichever its chambered for) field gage you toss the barrel and bolt as that pairing is at a dangerous level. Testing must be done with the ejector removed.

    Its not a good idea to swap bolts around. It accelerates wear on both the barrel extension and bolt decreasing service life of the barrel.

    While it IS possible to remove a barrel extension shave off justtttt enough material off the barrel chamber so everything indexes correctly again and the chamber to be reamed to spec. Ive never heard of anyone with the inhuman godlike skill to do it or the willingness to undertake such a feat of skill. Since at the end you will still have a rechambered barrel with a shot out bore. Cheaper to buy a new barrel for a couple hundred than spend a thousand or more trying to rechamber a shot out barrel.
     
    Last edited: Feb 11, 2013
  20. fsted2a

    fsted2a New Member

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    I am going to agree with Jon on this issue. Replacing parts is cheaper(and safer) than the catastrophic results if you are wrong. If you aren't sure, take your rifle to an experienced gunsmith. And whatever you do, don't get cable TV. You will end up a homeless 50 year old without a girlfriend. :D :D