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.
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.
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.
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.
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.
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.
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.
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.
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.
