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Thread: Mk18 mod 1 / CQBR build please advise

  1. #11
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    For the cost, I'd keep the 6720 as a mule upper (training, other uses) and pick up an SBR upper (and run it as a dedicated suppressed unit maybe - at least set it up around being a suppressed SBR capable setup).

    A 6933 upper with a Centurion C4 Cutout rail would be my SBR upper of choice if you want to go pure Colt. You then have a quality lower, and two uppers. One 11.5" you can use with or without a can, a a training/portable/high round count/lightweight 6720 upper to use in the interim, and continue using.

    If you want outright best can for part time on part time off, Surefire without a doubt. For a mostly suppressed upper, the AAC is the best value hands down, though an 11.5" opens up a full range (to a Titanium dedicated thread on, to an old school OPS Inc reflex can) For the money, though I'm not an AAC fan, it's incredibly hard to beat a 6933 and AAC 91t M4-2000.
    Last edited by TehLlama; 03-21-12 at 01:51.
    عندما تصبح الأسلحة محظورة, قد يملكون حظرون عندهم فقط
    کله چی سلاح منع شوی دی، یوازي غلوونکۍ یی به درلود
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  2. #12
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    I believe the real M4A1 CQBR uses a government profile barrel, not a lightweight barrel. Granted, the barrel is barely visible in the configuration of this rifle.

  3. #13
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    Swapping barrel for a colt 10.3 from saw. When stamp clears.

  4. #14
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    Good. That way you don't have to worry about enlarging the gas port.

  5. #15
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    Yeah and after doing some reading looks like it would be better to swap colt gas block for the badger ordinance block.

  6. #16
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    Quote Originally Posted by N.Franklin View Post
    Mine had extraction issues right out of the box, BCM extractor upgrade fixed it. If I were to do it again I'd have bought a Colt 10.3 upper and did the conversion myself.
    What kind of extractor spring/insert came with your DD MK18 URG? Did you add an O-ring from the BCM extractor upgrade kit?

  7. #17
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    The spec gas block would be either a Daniel Defense or Badger Mk12 gas block. The gas port isn't correct from the factory either, it needs to be opened up to .070" if it's not already there, .062" will be under-gassed.

  8. #18
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    Thanks for the heads up. I didn't know the badger gas block needed to be opened up. Almost have everything ready minus block, barrel and tax stamp.... Now I got to sell all the colt talo editon parts.

  9. #19
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    The Badger block and the DD block are both .750", but the finish on the interior of the part makes it too large to be a slip on solution, so you generally have to hit the Badger part with a drill press and a 3/4" bit. The DD part will usually only require some sandpaper to take the finish off.

    The gas port on the barrel itself needs to be .070", the block only requires opening up the main channel to .750" so it fits on the barrel correctly. They're both set screw designs, not taper pins, so it's a good idea to find someone to do the work for you, I HIGHLY recommend High Caliber Sales. Alan Brown assembled thousands of these rifles while he worked at Crane. Going with an experienced smith that has experience with the platform you're trying to clone is going to pay dividends, if only for the peace of mind knowing that it was done right and will run like a raped ape.

    My $.02, of course YMMV.

  10. #20
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    Quote Originally Posted by ClearedHot View Post
    What kind of extractor spring/insert came with your DD MK18 URG? Did you add an O-ring from the BCM extractor upgrade kit?
    Standard M4 extractor spring and insert came with it, I used the o-ring simply because I have about 10 of them laying around with only 2 springs and inserts left. Gotta use them up.

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