AR trouble

[barber613]

Not seeing any signs of gas leaks on bolt, but I have recently cleaned the entire gun. Yes wolf steel case ammo was used, however it has also happened with lake city. Don't see anything around the sight base either. Upon closer inspection, with the upper upside down, the gas tube is slanting. In addition the key appears to be crooked. What the hell, I got screwed.

 

[JosephR]

Does the gas tube have the normal kink in it? It starts out parallel to the barrel, bends UP and goes parallel with the barrel parallel again until it enters the upper. It's supposed to do this.

Can you take a picture of the gas key? Does it wiggle or wobble?

If the rifle goes into battery and fires, the key can't be too crooked and neither can the tube.

Where are you at in IN?

Is there anything stamped on the face of the buffer?

 

[barber613]

Took hand guards off and the gas tube itself is dirty on the outside on the ends. Is some gas leak normal? For some reason I can not post pics. the key does not wiggle, can take pics, but can not post pics. nothing on the buffer. It does have a four position stock, does that change anything. The buffer is not the same as my other with a full stock. Live in Kokomo.

 

[JosephR]

PM sent

 

[Cpt Caveman]

Fill us in. I'm interested in knowing what the trouble turned out to be.

 

[JosephR]

Still not resolved. The gas tube is very dirty...

 

[TheGhostRider]

Sounds like a short stroke problem. Even though the upper is a Colt it could be a bunch of Colt parts slapped together by a monkey.
This does not mean it's junk... it just needs the attention of someone who knows what they are doing!
Get rid of the lower... I'm not trying to be a dick! BUT, the lower will let you down sooner rather than later.
As for the cycling problem.... Gas, or the lack thereof.
Put one round in a mag, fire it.... if it doesn't lock back on the empty mag it probably is a loose carrier key. This can be fixed easily by re-torquing the key bolts and staking them. If you have problems with the gas tube leaking... which is rare... this can be fixed easily as well. Just replace the gas tube.
It sounds like you have some help from JosephR so you should be ok.
Good luck.

 

[techres]

Only cheap fix I could add would be to spray carb cleaner down the gas tube and let it run out of the barrel, wait a moment and then follow it with compressed air and then a AR pipe cleaner. I have done this in my Bushmaster with success to solve something very similar to your experience.

Don't bail on the equipment yet. Working through a new upper is frustrating as hell. Makes you want to just sell it off at a loss and be done with it (I have been there myself and done exactly that). Even better is the feeling of fixing the problem and having a good upper that did not "beat you" as it were.

 

[bullet293]

make sure you have the short buffer and spring in the car stock. did you sell that wasr yet?

 

[barber613]

Got out and shot some today. I took my good colt ar and the problem ar and switched the uppers and lowers. The problem did not stay with the vulcan lower. Again the vulcan lower paired with my proven good upper worked great. The issue appears to be with the colt upper that came with the vulcan lower. The bolt seems to move correctly in the carrier, which seems to move free in the upper. Gas problem? Will try to use the carb clearner. If that does not work, how do you change the gas tube and get it to seal?

 

[techres]

Got out and shot some today. I took my good colt ar and the problem ar and switched the uppers and lowers. The problem did not stay with the vulcan lower. Again the vulcan lower paired with my proven good upper worked great. The issue appears to be with the colt upper that came with the vulcan lower. The bolt seems to move correctly in the carrier, which seems to move free in the upper. Gas problem? Will try to use the carb clearner. If that does not work, how do you change the gas tube and get it to seal?

Gas tube swap instructions are about half way down on this page:

Assemble your own LOWER, UPPER, FREE FLOAT, TRIGGER, GAS BLOCK - Step by step instructions!

Try and keep the carb cleaner off of the Upper's finish as it might discolor it. Do not leave it on too long either. This is a trick I got from a gunsmith but not a solution I have read in a book. Arsenal, inc by the way has a thing in the warranty against using rough cleaners but I don't have any safe queens personally...

 

[techres]

Oh, and give the BCG a good cleaning too with a focus on the tubing, etc. Did the BCG come with the upper?

 

[KDUBCR250]

Switch the BCG into the proven upper this will further isolate the problem . If it still has the same problem Id say it a gas issue maybe the gass tube or even that the front sight post isnt lined up with the gas port Thats my

 

[barber613]

That website is very informative. Thank you.

 

[barber613]

What is the bcg

 

[techres]

What is the bcg

Bolt Carrier Group. I.E. the doohicky that looks like this:

 

[KDUBCR250]

What he said ! ^

 

[barber613]

As soon as I hit post, I figured it out. Two seconds to late. Dooh!!!!!!

 

[JosephR]

It's going to be the front sight base and a leaky tube. I still haven't gotten his pics up but his gas tube is FILTHY behind the front handguard cap.

 

[barber613]

Are you saying that the sight base itself could be bad, or just the tube?