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Thread: Max gas tube length for 14.5" barrel?

  1. #11
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    I believe the problem with the middy's had to do with the proximity of the gas port to the muzzle. IIRC the close proximity causes premature errosion in the gas port hole.


    This info was incorrect. The short gas system is the one that is known to have gas port issues
    Last edited by zydeco76; 02-23-09 at 00:27.

  2. #12
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    Quote Originally Posted by carl15 View Post
    Didn’t a very prominent moderator here say it was a clue that people were going away from 14.5 middys do to problems ?
    I believe I've seen something like that, either here or on a different website, but no specifics or sample size were provided. I've read on this website not to use an excessively heavy buffer with 14.5 middys, especially in cold weather.

    To date I've only read reports from individual users, most of them with sample size of 1 or 2, and I've not found negative reports so far. I've not seen large sample size-large volume of fire reports.

    Gas port on 14.5 middy is over 5 inches away from muzzle, which similar or longer than most SBRs. Are SBRs more prone to gas port erosion?

    I've recently had one of my 16 inch middies cut down to 14.5 as an experiment. So far so good, but the round count is low. I plan on taking through what is supposed to be a voluminous round count class, we'll see.

  3. #13
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    I had a 16" LMT MRP barrel w/middy gas system that I had cut down to 14.5". I put over 6k thru it since having it chopped, and never had a cycling or reliability issue that was caused by the barrel/gas system combo.

    I got rid of it last year, and the current owner recently told me that it still runs like a top. I replaced it with a Noveske 14.5" Afghan middy which so far has been 100%
    Last edited by nickdrak; 02-22-09 at 20:16.

  4. #14
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    Quote Originally Posted by zydeco76 View Post
    I believe the problem with the middy's had to do with the proximity of the gas port to the muzzle. IIRC the close proximity causes premature errosion in the gas port hole.
    AFAIK, this is not quite right. The problem with the proximity to the muzzle is not enough gas pressure for not enough time and short-stroking as a result. AFAIK, most 14.5" midlengths have larger gas ports to make up for this.

  5. #15
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    Port size

    I ordered a 14.5" Mid Length Gas Stripped Barrel manufactured by Sabre Defense Industries. I will measure the port size before I build it up and report back.

    Thanks for all of the replies!

    John

  6. #16
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    Quote Originally Posted by Bimmer View Post
    AFAIK, this is not quite right. The problem with the proximity to the muzzle is not enough gas pressure for not enough time and short-stroking as a result. AFAIK, most 14.5" midlengths have larger gas ports to make up for this.
    Indeed. The previous reply doesn't make sense at all. The farther away from the chamber, the lower the port erosion rate as I understand it.

    Port erosion is a carbine gas system issue. And from what some of the Armorors here have stated it's somewhat self limiting.

    There's more than enough barrel past the port on a 14.5 middy to make it run right. Shit. I've seen 16" barrels with a rifle gas system that will work.

  7. #17
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    New to M4Carbine, but have been lurking for quite a while. This is my first post here. I was glad to see this thread come up.

    I recently finished a build using a 14.5" CMMG lightweight midlength barrel. It was everything I hoped it would be for weight. Problem is, it would not cycle when I took it out to shoot for the first time. The bolt cycles far enough to cock the hammer, but does not eject or load any subsequent round. I am quite certain this is attributable to a gas problem.

    I checked the bolt carrier key for proper installation. It appears to be properly aligned with the gas tube and is not binding. The gas tube is pinned and does not appear to be leaking. Gas rings are properly installed - I checked the bolt and bolt carrier in another gun and it functioned fine.

    The only two possibilities I can think of are 1) ammo (I was using the .223 Centurion ammo bought from Aim - I will be trying LC M193 next time out), and 2) problem with the gas port. This is my sixth build, and I have never had a problem with a gun functioning properly. I have used CMMG on two other rifles and never had a problem. Any input would be appreciated.
    Last edited by 1811guy; 03-01-09 at 17:51.

  8. #18
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    1811guy,
    I really think the Centurion ammo is the problem. I put thousands of rounds of M193 through a CMMG 14.5" mid-length and never had a malfunction.

  9. #19
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    I don't agree. I haven't heard a single issue with Centurion ammo. The same can not be said for CMMG.

    Centurion is plain jane .223, and it should run.... especially on a middy.

  10. #20
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    I think the problem is not with CMMG's parts, but with their QC post/during assembly. I've seen multiple problems on multiple CMMG guns that could have been avoided by a 30 second scan of the gun, and were immediately spotted by the buyer. Hell, they sent me mine missing parts.

    CMMG makes great parts. These days, that's as far as I'd trust them...in my house, CMMG is a four letter word.

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