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Thread: Expert Knowledge Needed

  1. #11
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    Quote Originally Posted by KevinB View Post
    When the FF tube went on it -- what sort of gasblock is on it? did you change the pinned on FSGB?
    I reused the stock Colt FSB with tapered pins. I've actually pulled the FSB off a 2nd time, scotch brited the gas tube, and reinstalled it. I went out and put about 15 rounds through it and it's very apparently leaking from around the FSB/gas tube connection. It will function in semi if I use hot handloads, Privi 62 grain will work but it won't lock the bolt back on the last round, and lower loads won't function enough to load another round.

    The gas tube was pretty tough to get out the first time, I had to lightly grab it with pliers and twist it to get it started. Now it slides in and out fairly easily but it looks fine, no dents, cracks, or anything else. I ran pipe cleaners through it and it was and is clean. I've got a new one on order thinking maybe there's something I'm not seeing. Does anyone know of something I can glue the new one in with to seal it in... high temp silicone maybe? I don't want to get anything in the ports though so it will be a touchy operation if I decide to give it a shot.

    Thanks guys,
    J.T.

  2. #12
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    Regardless of what the Canadians did to their weapons, my Colt instructor told the class that it will cause problems just like you are experiencing. Since he has been affiliated with Colt for over 10 years, is one of their largest distributors on the west coast, I tend to believe him. If the problems were not present prior to the mod, I would guess that there was an effect.

    Also, cleaning the gas tube with a pipe cleaner will do nothing but give you slightly dirty pipe cleaners. Since the carbon is super heated in the tube it will not come out unless you use something (chemical) to loosen it up.

    With an M4 set up you have to realize that the dwell time is shorter and more violent due to the gases moving faster through the shorter barrel and then the gas tube returning back to the bolt carrier key. With a rifle it is the opposite because of the longer barrel and gas tube. If you used the correct punch to remove the gas tube pin, then the hole should not have gotten enlarged. Was the gas tube you put in, new or used? Did you re-use the same roll pin? (not recommended). Also, you should generally not re-use any type of roll pin, FSB pins or anything else. They are almost always consider one use items. That is the rule for every armorer school that I have been to.

    Is the gas tube straight and mating up to the bolt carrier key properly?
    What kind of ammo are you shooting? There are alot of variables that come into play. You could always put it back into its' original configuration and then see if the problem persists.
    BTW- Why did you Scotch-brite the gas tube???

  3. #13
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    Quote Originally Posted by Iraqgunz View Post
    Regardless of what the Canadians did to their weapons, my Colt instructor told the class that it will cause problems just like you are experiencing. Since he has been affiliated with Colt for over 10 years, is one of their largest distributors on the west coast, I tend to believe him. If the problems were not present prior to the mod, I would guess that there was an effect.

    Also, cleaning the gas tube with a pipe cleaner will do nothing but give you slightly dirty pipe cleaners. Since the carbon is super heated in the tube it will not come out unless you use something (chemical) to loosen it up.

    With an M4 set up you have to realize that the dwell time is shorter and more violent due to the gases moving faster through the shorter barrel and then the gas tube returning back to the bolt carrier key. With a rifle it is the opposite because of the longer barrel and gas tube. If you used the correct punch to remove the gas tube pin, then the hole should not have gotten enlarged. Was the gas tube you put in, new or used? Did you re-use the same roll pin? (not recommended). Also, you should generally not re-use any type of roll pin, FSB pins or anything else. They are almost always consider one use items. That is the rule for every armorer school that I have been to.

    Is the gas tube straight and mating up to the bolt carrier key properly?
    What kind of ammo are you shooting? There are alot of variables that come into play. You could always put it back into its' original configuration and then see if the problem persists.
    BTW- Why did you Scotch-brite the gas tube???

    I'm guessing it's not a recommended mod either, in theory it makes sense that it should at the very least have a custom buffer/spring. I only ran the pipe cleaner through to make sure there were no blockages where carbon had possibly been knocked loose. All of the parts were reused however I don't feel there are any issues with the pins, what can I say, it's a feel thing. They're all holding tight and there aren't any gas leaks between the barrel and FSB. I'm concerned with both ends of the gas tube, I don't like lack of ANY drag between the gas key and tube. It will run with good ammo on the 5.56 chamber pressure levels, I just want it to run with all ammo, regardless of whether or not I use it commonly. I may have to just accept specific ammo to make this combination work. Oh ya, I scotchbrited the tube to make sure what I was seeing was gas residue and not some leftover CLP or something - kind of like using flour to look for the wet spot.
    Thanks for the input,
    J.T.

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