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Thread: Max gas tube length for 14.5" barrel?

  1. #31
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    Quote Originally Posted by jmart View Post
    Don't all those run shaved gas blocks under the HGs, either carbine or middy?
    Nope. Some do, but several guys over there just cut the barrel down.. and maybe opened the port.

  2. #32
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    Quote Originally Posted by trinydex View Post
    i thought the definition of a dissy was a barrel that used an fsb at rifle length but used a carbine gas (didn't ever understand why it wasn't a middy gas).
    That is the original formula. At the time, middies weren't too well known. And in my opinion, you're right. The middy is the much better way to go. That's what I'm building right now.

  3. #33
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    Funny. I thought the definition of a dissipator was a barrel as short as would run reliably with a rifle-length gas system, so that much of the recoil was "dissipated".

  4. #34
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    Well, it seems to run fine with LC M193 ammo. I would prefer it works with .223 ammo as well given that LC M193 does not grow on trees anymore. Would opening the gas port up help any? Or should I just leave well enough alone?

  5. #35
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    I'd get it checked out. It should easily run .223 ammo. I wouldn't just open the port without determining for sure that it was needed.

  6. #36
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    Here is an update on the rifle:

    I was unable to get any response from CMMG customer service by e-mail or phone. I decided to remove the FSB to see if there was any visible problem. While trying to drive our the taper pins I learned that CMMG does not use hardened steel pins. The pins were like butter and despite my best efforts and care they just became more and more deformed. I finally took a 1/16" drill bit and bored a hole half way through the pins. It was like drilling through aluminum. I then used the same drill bit as a punch. This put the driving force of my hits lower on the pins and they finally came out.

    I could see where gas was leaking from the port under the FSB and toward the handguards. I surmised that because the CMMG pins were so soft, they were unable to make a tight seal between the barrel and FSB. The pins essentially push down on the FSB and up on the barrel creating a tight seal. The CMMG pins were doing nothing more than holding the FSB on. I re-attached the FSB using Colt pins I ordered from Brownell's. The pins were noticeably better in quality and while being driven in did not squish in place like the CMMG pins. Back to the range - cycled the .223 ammo without a problem.

    While I will never buy another CMMG product again because of their customer service, I do feel that the barrel is decent - I get good groups with it, and it is made from CV steel. The FSB is F marked - looks to be a standard mil-spec part. The permanently attached FH was done properly and is properly timed. Headspacing is right on. I am a bit confused as to why CMMG would use something other than a mil-spec taper pin given that it is such an inexpensive part.

    If I could have found another company that makes a lightweight 14.5" midlength barrel I would have considered them. The closest I could find was Noveske, but I wanted a lightweight profile. Live and learn.
    Last edited by 1811guy; 07-02-09 at 09:51.

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