AR15 Failing to Cycle

[Mac Attack]

I had my Colt preban AR15 for over 5 years but had never fired it in it's full load .223 until this past weekend. Up until last weekend I had fired my AR15 on numerous occasions with a .22 conversion kit without any major issues. But this weekend when I tried shooting it with .223's (5.56 Cal) I had failures to cycle. I tried shooting with different mags and different loads and it still wouldn't cycle other than by hand. I noted that I did not hear the spring compress on my collapsible stock. I am sure that I have the proper spring recoil buffer (?) because it came with the stock.

I don't know if this would cause it but the bolt and upper receiver were fairly dry. I have heard that shooting .22 LR's can be very dirt and can foul the gas tube but I don't know how to check this. Is there a way to remove the gas tube and which is the best way to clean it? How do I fix this issue?


Mac

 

[gamachinist]

The Gas tube may be clogged,or there may have been a problem with it's alignment from it's original assembly.

The first thing to check for is a blockage of lead from the rimfire bullets over the port in the barrel.Since it was a new gun,it could have had a burr there that would have been removed by the first jacketed bullet,but collected up enough lead from the rimfire bullet to obstruct the hole.

If you have access to compressed air,use a "blow gun" to blast air through the tube from the back end of the tube.Do this dry,or it will make an even bigger mess!
There are also some long pipe cleaner type brushes for cleaning the tube.

If you have to remove the tube,there is a small roll pin in the front sight base that holds it in place.
Remove the handguards,drift out the pin,and remove the tube to the rear,out the back of the upper reciever.Sometimes they are very tight,so be careful about using pliers to grip it as it will bend or flatten it out.There is a small tool made to remove it that grips it around it instead of just on the sides.

There have been some guns with misaligned holes in the barrel and front sight base,as well as misdrilled holes in the front sight base itself,where they don't meet up completely,as well as burrs left behind blocking the flow of gas into the tube.It could be any of these problems.

I hope this helps,Robert.

 

[Mac Attack]

Robert thanks for the advice. I will try to blow out the tube first with compressed air in hopes that it is blocked with lead. Hopefully that is all it is.

Mac

 

[1911Tuner]

Jammin' Jenny!

Check the bolt carrier key to see if it's tight...Best guess is the
rimfire/lead/gas tube thing, but it could also be in the gas block or the port itself. If it is, have fun! Lead ain't compatible with any gas system. The
marketers of the conversion kits sometimes fail to mention that little fact.

Luck!

Tuner

 

[Mac Attack]

Okay I tried to clear any obstructions in the gas tube via air compressor but nothing came out. I looked down the barrel every which way and could not see a hole in the barrel for the gas tube. I then tried blowing some WD40 through the tube from the upper receiver in hopes of seeing some fluid go through the tube into the barrel but did not see any. I tried drifting out the pin holding the gas tube in place but didn't have the right tools and didn't want to break anything. If I do have an issue with hole alignment/no hole for gas tube how do I fix this?

Regarding the tight bolt in the bolt carrier. I did notice that the bolt fit is fairly tight in the bolt carrier. Could this be the issue? I haven't had a chance to oil down the entire gun and test fire but I hope that this is the problem and not the hole in the barrel issue.

Thanks.

 

[gamachinist]

Mac,
The bolt fits fairly tight because of the sealing rings on it(look at an exploded diagram of the bolt).
The hole in the barrel is very small,and if you could see it looking down the bore,that would be a problem!
After you get the gas tube out,then it will be easier to find out where the problem lies,the tube,in the front sight base or in the barrel port itself.
You said you were having a problem with removing the gas tube.Were you able to get the pin out?

If it is a burr or hole not drilled deep enough in the sight base,a drill bit will fix that.
If it is a clogger barrel port,the sight base will have to be removed and a small drill bit or possibly even a stiff piece of small wire used to clear it out.

Hope this helps,Robert.

 

[Black Snowman]

It sounds like it's a gas issue all right. With no fluid leaking into the barrel it's either clogged up GOOD or mis-drilled somewhere. Did you have a rubber fitting for the air gun so that it sealed in the tube? If so did you hear air leakingout? If not you might want to find and try blowing it out again before getting too crazy.

FYI: It's almost imposible to see the hole. My DEagle has 2 big gas holes in a large and spacious barrel and the only way I could find them was feeling around with a pick. No amount of light, angle, or mirrors helped me find them. One little hole deep in a .224 barrel is much worse to locate, much less determine if it's clogged.

If you aren't comfortable tearing it apart that's probably a good sign that you may indeed break something. Might be worth taking to a local smith if they can get you done pretty quick.