New to me gun show AR wont cycle....

[IronMonster]

So I picked up an AR at a gun show, It was built with mostly good parts, Noveske lower and "keyhole" upper... the only questionable bit is a unstamped barrel... (I know there are some reasonable barrels that are not stamped but i just dont like the fact its not)..... I took it out this weekend and the gun wont cycle. The bolt does not move at all.. I was using steel case ammo ( all I took out with me unfortunately ) but its not a feed/jam situation. It could be fired and the spent case ejected and a fresh round loaded with a tug on the charging handle.... The only thing that I can think of is the gas port on the barrel is not timed to the gas block... I have never had a barrel out of a AR and I dont really know how they mate there but I just cant imagine that if gas was present even a little in the action that the bolt would at least jump or wiggle or something... but far as I could tell it was locked shut.... bolt and carrier are properly assembled and move freely in the upper.. plenty of lube.... Anything I am overlooking?

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[halmbarte]

You assume that there is a gas port....

H

 

[mattt]

Couldn't you chamber a round, then close the dust cover on the ejection port. If the bolt moves enough to pop the cover open you know its tryin to work. What weight buffer are you using? A heavy or H2 buffer mixed with under powered steel case ammo might not work well together.

 

[OR4X4]

Could be a cheap barrel with no port, undersized port, or mis drilled port so that it is not lined up, could be the gas block is crooked after tapping in the retaining pin.
If it is not stroking at all I would assume no gas present, If it is short stroking then port diameter or alignment is bad is where I would look first. Another easy and frequent issue that causes short stroking is that the gas key on the bolt isn't tightened all the way.

M4 or rifle length?
If the dust cover pops open, try 69grain ammo.

 

[The B]

There's definitely something drastically wrong..

Check:
Carrier gas key - present, and two tight, staked bolts securing it to the carrier
Gas tube - present, connected and pinned to the gas block
Gas block - doesn't rotate, fasted (whatever kind or type, I don't know what you have) not a huge amount of carbon blast residue stuck to barrel at the seam
Gas port - pull upper, pull bolt-carrier assembly, shine light in through back, look down barrel, you should be able to see it below the gas block

Gas rings - present at bolt tail - good lookin' out, bmgm

 

[bmgm37]

Have to ask, are there gas rings on the bolt? What kind of gas block is on the barrel, pinned or set screw, a pic would help.

 

[IronMonster]

You assume that there is a gas port....

H

Right, and that did cross my mind.... I dont know how you could check other than tearing down the rifle

 

[IronMonster]

Have to ask, are there gas rings on the bolt? What kind of gas block is on the barrel, pinned or set screw, a pic would help.

Yes the rings are on the bolt.... I dont have a spanner to take off the forearm but I am pretty sure that I can see two set screws on the bottom of the gas block and then a roll pin on the top at the gas tube.

 

[IronMonster]

There's definitely something drastically wrong..

Check:
Carrier gas key - present, and two tight, staked bolts securing it to the carrier
Gas tube - present, connected and pinned to the gas block
Gas block - doesn't rotate, fasted (whatever kind or type, I don't know what you have) not a huge amount of carbon blast residue stuck to barrel at the seam
Gas port - pull upper, pull bolt-carrier assembly, shine light in through back, look down barrel, you should be able to see it below the gas block

Gas rings - present at bolt tail - good lookin' out, bmgm

Nope, all parts accounted for and present... gun is fresh assembled and no gook of any kind

 

[IronMonster]

Sounds like I need to find a spanner wrench to get the forearm off and see if I can get the gas block off.... I'll report back and tell what I find.

 

[PBinWA]

Take the bolt assembly out. Stick a spent round in the chamber and hold it in with your finger. Blow air down the barrel from the muzzle ( air compressor or some other method) and you should be able to get decent air flow out of the gas tube. The gas tube is the small metal tube above the chamber area. This is the easiest way to check basic gas port alignment.

 

[elsie]

Is there any carbon from firing on the bolt or in the receiver? If not, then you're definately not getting gas back to work the action.


elsie

 

[Mason3379]

My buddy had this same issue recently with a DPMS rifle that he bought. It was a pretty simple fix that his buddy who is a gunsmith fixed for him. Chances are your tolerances in the chamber are just a bit too snug. He had the same problem, gun fires, wont extract under its own power yet was fairly easy with the charging handle. Next round would chamber and problem repeated.

Good luck!

 

[IronMonster]

Is it necessary for the gas tube to actually fit into the gas key on the bolt carrier? I was looking at another AR and realized that the one in question does not have enough gas tube sticking into the receiver to actually mate with the gas key....

 

[bmgm37]

Uhhhh, it sounds like your rifle may not have a gas tube in it. You should be able to see the end of it when looking into the upper receiver. Pull the handguards off and see. Post up some pics of it if you can.

 

[The B]

Is it necessary for the gas tube to actually fit into the gas key on the bolt carrier?

yes

 

[deen_ad]

Exactly why I won't buy an "assembled" firearm at a show. I prefer ones of known quality since I'm a beginner with AR's.

 

[IronMonster]

Sorry for the crappy pictures.... The gas tube is present, I can clearly see it through the handgaurd... But it does not pass into the upper receiver but rather stops flush... Wrong gas tube? It does not look like its broken

 

[eldbillbo]

Wow, i don't see a gas tube. its got the wrong size gas tube . you should be able to see almost a inch of it in your receiver . thats you problem

 

[bmgm37]

Can't really tell by the pic, but it is either a broken tube or somebody installed a carbine length gas tube on a mid length barrel setup.