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Thread: Expert Knowledge Needed

  1. #1
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    Expert Knowledge Needed

    OK guys, this is my first post so I want to say thanks for all the awesome knowledge I've gained from reading the posts on this forum. Now here's my problem:
    I've got a Colt 20" HBAR that I decided to upgrade a bit. I put a DD flat top upper on it, vltor collapsable, and a JP FF rifle length tube... now it's short stroking. I can see it's leaking gas where the gas tube fits into the front sight post and a little can be seen between the barrel nut and receiver. I've ordered a new gas tube hoping it will fit tighter into the FSB and I'm wondering if this will be enought to get it back to it's former Colt self. A buddy thinks it could be a lockup timing issue, I think it's gas related but could also be complicated by the fact that I know have a carbine buffer and spring on a rifle. I need your thoughts, this was a perfectly functioning rifle before I screwed with it. The barrel and BCG are still original.

    P.S. On the bright side, due to the fact that I couldn't be without a perfectly functioning AR, I went out and bought a LMT M4 and it runs like a champ.

    Thanks in advance,
    J.T.
    Semper Fi

  2. #2
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    You removed the FSB in order to install the tube, right? Maybe you have a leak there between it and the barrel now. Dry a drop of loktite between the barrel and FSB. Steve at ADCO had to do this on a build I had done. The loktite capillaries into the crevasses and once dry works well.

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    Quote Originally Posted by SuicideHz View Post
    You removed the FSB in order to install the tube, right? Maybe you have a leak there between it and the barrel now. Dry a drop of loktite between the barrel and FSB. Steve at ADCO had to do this on a build I had done. The loktite capillaries into the crevasses and once dry works well.
    I've been thinking of doing just that, do you think it will help to loktite the gas tube into the FSB as well?

  4. #4
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    Be careful with the loktite. You do not want to seal up the gas port hole. I would imagine the pressure would blow it out but I can't say for sure.

    Leave the gas tube alone. Unless you pinched it or messed it up in any other sort of way I wouldn't look to it as the culprit. I've reused them several times on several rifles.

  5. #5
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    Here is what I can tell you. During the Colt Armorer course the instructor told us about an LE agency in Az. that did exactly what you did. When they went to the range they immediately started have malfunctions. He advised that he would drive out and a take look. First thing he asked is who did the modification? Someone said the PD armorer. He advised the reason they were malfunctioning is because of the long barrel/ with relationship to the short buffer spring/ buffer which ties into extraction and the cycling.

    He promptly busted out his tools, put one of the weapons back into the original configuration and the problems ceased. He advised us that you cannot take a rifle size weapon and do what you did and expect it to work. I am willing to bet that if you put a shorter barrel on the gun and did a full mod to make it into a carbine, assuming that all parts are correct and installed properly your gun would start working again.

  6. #6
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    That should be an easy test. Just slap on the old stock and see if it starts working.

  7. #7
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    FWIW - I am a Colt Armorer, however - I am by training a trigger puller not a armorer - I took it to increase my own knowledge.

    You should be able to add a telestock and carbine buffer and spring to a full lenght rifle

    The Canadian Forces modified their fleet of weapons to M4 stocks with H2 buffer.



    I was switching between a M2 Aimpoint, TA31 and EOTECH 552 for a bit.





    I did leanr not to mount the optic on the RAS - and that the PEQ is better off behind the front sight tower (I've broken some things repeatedly and it takes me few items to learn)

    The average soldier is issued a 20" barrel C7A2, Light/Airborne Inf and attachments are issues a 16" upper as well -- and SF elements have 10", 11.5, 14.5, 16" and 20" uppers --- all working off the same lower (or lowers for those issued a few guns.)


    I dont own any guns with fixed stocks - except ones with the Magpul PRS.

    Edit the only weapons sytem still with fixed stocks are the AR10's and the C7CT (a buddy just reminded me)



    and some guys have convinced the powers that be to alter some of them too.
    Last edited by KevinB; 02-18-08 at 08:55.
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

  8. #8
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    Quote Originally Posted by KevinB View Post

    You should be able to add a telestock and carbine buffer and spring to a full lenght rifle

    The Canadian Forces modified their fleet of weapons to M4 stocks with H2 buffer.

    Agreed, and that last picture looks great.

    I've seen people use the rifle length spring when making this conversion, and that has always shown itself to be a problem. With the proper spring and buffer, the weapons should run quite nicely.
    Stick


    Board policy mandates I state that I shoot for BCM. I have also done work for 200 or so manufacturers within the firearm community. I am prior service, a full time LEO, firearm instructor, armorer, TL, martial arts instructor, and all around good guy.

    I also shoot and write for various publications. Let me know if you know cool secrets or have toys worthy of an article...


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  9. #9
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    I used the spring, buffer, and buffer tube that came with the vltor stock. If it's not a gas leak issue (I'll put the old stock back on and find out for sure) why would it have problems short stroking with a lighter(carbine) buffer? Is the spring stiffer? Could I buy a softer spring? I guess I'm confused as to why a rifle uses the heaviest buffer if it's gas pressure is so much lower than a carbine.

    By the way, I know I'm a freak with the 20" barrel and a collapsable stock but I love the accuracy and recoil impulse from the rifle length set up. I actually run my rear sight toward the front of the receiver with the stock all the way closed and it's a lot more mobile than you'd think. It'll be a great set up if I can get it to run.

    Thanks for all the input,
    J.T.

  10. #10
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    When the FF tube went on it -- what sort of gasblock is on it? did you change the pinned on FSGB?
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

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