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Thread: MK18 MOD1 Technical Thread

  1. #31
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    Quote Originally Posted by ra2bach View Post
    can you remember specifically what and where you heard about this?

    I'm not jumping your shit but I really do want to get to the bottom of this DD gas port deal. what I'm hearing is a couple of discussions that get taken out of context and repeated on down the line.

    they may be or have been true in a specific instance but this is the type of stuff that can develop into an errornet "intelligence" dump - "Don't buy Daniel Defense, their gasports are drilled by the Devil!"

    also, just remember a 10.5" barrel should have a different GP size than a 14.5 or 16. are we sure we're comparing apples here?
    I remember 87GN stating a few things about the gas port dimensions. Maybe he can weigh in on the matter here. I won't be able to find the threads on TOS.

    And based on my limited experience with my buddy's LMT and my DD with nearly identical configurations. His cycles much softer and smoother. I'd still buy a DD barrel if I had to do it all over again. It handles and groups nicely. And I never had a malfunction out of it running it hard. So it is a very reliable upper.

    As far as the dimension for a Mk18, I know that they are different. Larger right? This is why I ask... I really want to buy a reliable upper that can run both suppressed and unsuppressed. I you or anyone else can school me on Mk18 gas port sizes, I'd be much obliged.
    Last edited by polymorpheous; 11-25-10 at 12:49.

  2. #32
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    mk18 port size is .073" or .070"... cant remember which. LMT's 10.5 port sizes are .073 or .070... cant remember which.

    which is close enough that i wouldn't give a rip- buy an LMT with confidence.

    you also need to take into account that the gas port size chosen by crane has some degree of arbitrariness to it- it's the size they chose, to see if it seemed to increase reliability, and it did, so it's what they used. they did not take it to infinity and beyond- it's not THE EXACT IDEAL gas port size.
    Last edited by bkb0000; 11-25-10 at 13:15.

  3. #33
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    Quote Originally Posted by bkb0000 View Post
    mk18 port size is .073" or .070"... cant remember which. LMT's 10.5 port sizes are .073 or .070... cant remember which.

    which is close enough that i wouldn't give a rip- buy an LMT with confidence.

    you also need to take into account that the gas port size chosen by crane has some degree of arbitrariness to it- it's the size they chose, to see if it seemed to increase reliability, and it did, so it's what they used. they did not take it to infinity and beyond- it's not THE EXACT IDEAL gas port size.
    This is very helpful.
    Thank you.

  4. #34
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    Quote Originally Posted by polymorpheous View Post
    I've bought a lower to SBR, saving the $200 now for the stamp.
    Come tax time I will buying an upper for it.

    Right now it comes down to the Noveske N4 basic 10.5", (bonus free lower!), and Daniel Defense's 10.3" Mk18Mod1 upper. (LMT may still be an option too.)

    Now my understanding is that the gas port diameter plays a huge part in SBR reliability, especially when suppressed.

    It is also my understanding that Daniel Defense is now a DOD contractor for the Mk18Mod1 uppers. However I've read that Daniel Defense gas ports are kind of all over the place.

    I have one of their 14.5" CHF M4 barrels and it seems over-gassed compared to my buddy's LMT 14.5 M4 barrel. We both run the same weight buffer, and I have a A2X flash hider and he is running a Phantom. I can't see that making a big difference.

    Any opinions on Daniel Defense's gas ports on these uppers?

    Please keep this thread to USGI MK18 issues. Please do not post about your personal build.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  5. #35
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    I checked with a buddy, who was a civilian armorer for the SEALs at a Virginia base. "Jon" said the following on the specs for the Mk 18 CQBR upper reciever:

    Upper Over All Length: 19.25"
    Over All Weapon Length: 26.25" Stock collapsed
    Over All with Stock Extended: 29.5"

    Barrel length: 10.3"

    Gas port is .070 versus .052 for M4A1

    Extractor mods include Crane "o" ring under extractor.

    Attached is a picture of a current US Navy Mk 18 Mod 1 from the AAC Silencer shoot along with some other US Navy issue gear.



    Standard Mk 18 on the Beach (US Navy Photo)
    Last edited by SpartanDCI; 12-09-10 at 12:54.

  6. #36
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    Here are most of the pics that show the rifle well that I have saved from the internet. At least two of them are Colt receivers and they appear to have Mk12 gas blocks.















    From Daniel Defense IIRC:


  7. #37
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    It is interesting how often I see these MOD1s with the old style Colt buttstock. It is pretty rare to even see them with SOPMODs.

  8. #38
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    Quote Originally Posted by BBB View Post
    Whats funny is FFGs have these being used for VBSS ops. Go figure. Maybe the NAV thinks these shorties better used below decks rather than in the mountains of A-stan?
    HOA ops may be different, but on the last two FFGs I've been on, it wasn't the ship's company that had the MK18's. The LEDET would bring the SBRs onboard. Ship's company usually had the M4.

  9. #39
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    I would like to bump this thread up for more info.

  10. #40
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    Is there any difference in the Mk. 18 guns, and the M4A1 CQBR upper receivers?
    We miss you, AC.
    We miss you, ToddG.

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