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Thread: Looking To Finally Do A Mk 18 SBR...

  1. #11
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    Quote Originally Posted by kaltesherz View Post
    Why don't you just pick up one of the new 11.5 BCM KMR uppers and throw it on that Bushmaster lower?

    I plan on picking up a 5.56 Saker in the near future to run on mine (once my Form 1 clears). It's extremely durable, quiet, and has a bunch of innovative features. Plus it's a bit cheaper than Surefire.
    Want to keep the Bushmaster "as is" for abusable work that isn't life threatening.
    It's hard to be a ACLU hating, philosophically Libertarian, socially liberal, fiscally conservative, scientifically grounded, agnostic, porn admiring gun owner who believes in self determination.

    Chuck, we miss ya man.

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  2. #12
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    Quote Originally Posted by kwilkin View Post
    Personally, my view is that the only thing "Mk18" on the DD offerings is the rail system.* Now that that's out of the way....

    Overall, I thing you would be better served with a Colt, BCM, or LMT SBR upper. The DD 10.3" barrel is now well-understood to be over-gassed for NATO-spec ammo. The gas port has been shown to be nearly .1" larger than spec. DD does this so that their guns will cycle with a wider range of commercial ammo. Shooting hotter loads in an over-gassed system will put additional stress on other components critical to smooth operation of the system. This means more regular maintenance/replacement of parts and the potential for unexpected failures. Add a suppressor on there, and the problem is exacerbated. This is not to say that there aren't many satisfied users of DD uppers.

    If you want a very close clone of an issued Mk18, I suggest picking up either a complete upper or just a MK18BA (barrel assembly) from Specialized Armament Warehouse. These are all Colt Defense parts and will be closer to spec. The downside is obviously cost.

    The LMT 10.5" upper is a good starting point for a Mk18 clone. The barrel is 10.5" instead of 10.3" but they will have a more appropriately sized gas port. Another advantage is that LMT 10.5" barrels have a slightly heavier contour under the handguards which adds additional rigidity while having a suppressor mounted which, in theory, should reduce POA/POI issues with a suppressor mounted.

    Both the LMT and SAW MK18BA assemblies will require you to remove the front sight base and install a Mk12/Crane-style/low-profile gas block to install the RIS II rail, so that is something to consider. Also, DD has temporarily suspended commercial sales of the RIS II rails (FDE) while they fulfill a military contract. So, the only way you are going to find that rail is on their complete uppers or rifles. I'm sure they will offer them again, no one knows when that will be, however.

    SureFire SOCOM and KAC NT4-QDSS suppressors are correct (i.e., issued) for the M4/M4A1/Mk18/CQBR and will both be suitable/warrantied for use on 10.3" barrels and will clear the rail. AAC suppressors, as is my understanding, need additional clearance on a 10.3" barrel with the RIS II, so a 10.5" barrel is recommended for those. I'm not sure about other suppressors as I'm a clone guy and try to stick to spec.

    There is some debate about the optimal SBR length. Some people like to go short as possible, while there is evidence that supports 11.5" as a more optimal length. So, you have to balance how accurate you want to be with parts availability, cost, and which suppressor you plan to use.

    *Note also that the "Mk18" is a specific military designation for a particular type of weapon. What DD is offering is actually a clone of M4A1 Block II CQBR (close quarters battle receiver). DD has, in my opinion, hijacked these military designations for marketing purposes to sell to the uninitiated. For example, their "Mk12" is anything but with the exception of 18" barrel profiled for an Ops-Inc suppressor and, like the "Mk18," their M4A1 doesn't have the proper RO921HB-profile barrel. I feel compelled to point this out, although most people don't seem to care about such issues.
    OK, looks like I need to re evaluate my options.

    Wish BCM offered a factory 11.5 SBR in a Mk18 "style."

    Another thought, if I'm running plain jane .55 grain 5.56, would I be better served by the DD Mk18 and it's larger gas port?
    It's hard to be a ACLU hating, philosophically Libertarian, socially liberal, fiscally conservative, scientifically grounded, agnostic, porn admiring gun owner who believes in self determination.

    Chuck, we miss ya man.

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  3. #13
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    One of the issues with the larger gas port on the DD 10.3 barrels is that the far side of the port catches a bit of the copper jacket and causes premature wear. There's a power point presentation floating around with a cross section of a worn barrel showing major erosion and collecting of copper fowling.

    I don't know if this is a problem with other brands of 10.X barrels (Noveske, LMT, etc), or if it's solely caused by the ginormous DD gas ports.

  4. #14
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    I have a DD 10.3" barrel on one of my SBR's, and run it suppressed with a SWR SPECWAR 5.56. I have a H2 buffer with heavy Wolff Buffer spring, and haven't had a lot of issues with wear and tear; the only issue I had is a lot of gas shooting with a BCM Mod 4 Gunfighter Charging Handle. However, I will admit that I have not run as many rounds as others have had since I left the SBR's/suppressors in my Florida Trust when I moved to California for work

    I will hopefully have some property in Nevada soon, and want to move all my NFA items west. Reading about the over-gassed issues on DD 10.3" barrels give my pause, especially since it beats up a lot of internal parts. I may switch out the barrel to a Colt 6945, LMT 10.5" upper, or KAC URX 11.5 upper but may shoot the upper and replace it after I shot it out. The only issue I have is not to damage my suppressor, but so far no issues. I have had one FTF with American Eagle 55 grain FMJ round, and I shot that magazine by mistake. I usually shoot Speer Gold Dot 64 grain without issues.

  5. #15
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    Quote Originally Posted by SteyrAUG View Post
    OK, looks like I need to re evaluate my options.

    Wish BCM offered a factory 11.5 SBR in a Mk18 "style."

    Another thought, if I'm running plain jane .55 grain 5.56, would I be better served by the DD Mk18 and it's larger gas port?
    They do, actually... And they have it in stock!

    http://www.bravocompanyusa.com/BCM-1...risii%20de.htm

  6. #16
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    Quote Originally Posted by Col_Crocs View Post
    They do, actually... And they have it in stock!

    http://www.bravocompanyusa.com/BCM-1...risii%20de.htm
    Looking for a complete factory SBR, not just an upper.
    It's hard to be a ACLU hating, philosophically Libertarian, socially liberal, fiscally conservative, scientifically grounded, agnostic, porn admiring gun owner who believes in self determination.

    Chuck, we miss ya man.

    كافر

  7. #17
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    Quote Originally Posted by SteyrAUG View Post
    Looking for a complete factory SBR, not just an upper.
    If you have any contacts or dealer with acusport they are clearing out factory DD mk18's for not much more than the upper.
    I paint spaceship parts.

    Quote Originally Posted by Failure2Stop View Post
    Stippled Glocks are like used underwear; previous owner makes all the difference in value.

  8. #18
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    Quote Originally Posted by VIP3R 237 View Post
    If you have any contacts or dealer with acusport they are clearing out factory DD mk18's for not much more than the upper.

    I'm a FFL and can get a DD Mk18 for dealer price from a few places, but it sounds like the DD rifles have issues I need to avoid.
    It's hard to be a ACLU hating, philosophically Libertarian, socially liberal, fiscally conservative, scientifically grounded, agnostic, porn admiring gun owner who believes in self determination.

    Chuck, we miss ya man.

    كافر

  9. #19
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    Steyr have you considered a Colt 6945? It has a factory 10.3" cold hammer forged barrel that is a slightly heavier profile than the 6933 and uses Colts monolithic chassis.

  10. #20
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    Quote Originally Posted by JoshNC View Post
    Steyr have you considered a Colt 6945? It has a factory 10.3" cold hammer forged barrel that is a slightly heavier profile than the 6933 and uses Colts monolithic chassis.
    Pretty much the rifle I'm trying to buy. Only problem is Colt seems to want to keep it out of the hands of most wholesalers and I'm not ready to pay SAW/Clydes prices when I know what the FFL price is. Seems even 6933s are no longer available through suppliers I've used for years now.

    It's just becoming too much work to try and buy a Colt SBR at FFL pricing. Meanwhile Daniel Defense Mk18s are everywhere for $1,200.00 in stock and ready to roll. I'm gonna try a few more sources Monday for a Colt 6945 but if they prove to be unobatnium at dealer price then I'm just grabbing the DD.
    It's hard to be a ACLU hating, philosophically Libertarian, socially liberal, fiscally conservative, scientifically grounded, agnostic, porn admiring gun owner who believes in self determination.

    Chuck, we miss ya man.

    كافر

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