AR cycling issue

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oldschool45

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I picked up an A2 style AR with a 20" barrel from a local pawn shop lets call it close to dirt cheap. I like the accuracy I got out of it but it didn't cycle. The shop gunsmith took a crack at it and replaced the BCG group with a Nickel Boron one. It no cycles but not 100% of the time. He says he got 15 rounds cycling fully.
I don't care to take it back again and its not going to be a home defense gun so perfect reliability isn't a concern.
Some thoughts; I'm using brand new 10 & 30 round Pmags. Would moving to a lighter buffer or spring help?
Thanks,
 
Start with a good detail strip and cleaning. Pay special attention to the gas tube and block. Inspect gas rings and gas key for tightness. Then get back to us.
 
I not much of an ar pro but have you checked the gas system / tube ?
I believe the buffer may be stamped with a letter / number
Since its from a pawn shop you don't know if it's been messed with it is possible that it's has
A non stock buffer and spring
 
Give it a good clean....Scrape the rear of the bolt after you disassemble it....Not the Bolt carrier group but the bolt itself......Sloppy wet lube it (Drowned the thing!!) and see what happens.....I shoot full auto and have problems with dry bolt after 2 40 round mags...Drowned it in your favorite mid weight lube an give it a go? i get 400 to 500 rounds out full auto by preparing ahead of time before firing
 
As far as the gas rings go do this: Dismantle and clean the bolt and carrier. After it's really clean put a few drops of oil on the gas rings. Assemble the bolt to the carrier and extend the bolt to it's outer most position. On a level surface, stand the carrier up with the bolt facing down. If the bolt does not slide back into the carrier the rings are good. If the bolt slides back into the carrier, replace the rings.
 
Ok, the gas tube got replaced with the BCG and it got a through cleaning. Would going to a carbine weight buffer help even at the cost of a little recoil and wear.
Ammo was surplus XM193 and new Aquila 5.56x45 both reloadable brass
Gas key is firmly staked.
joem1945 I will test the gas rings tomorrow when I take a quick look at the rifle
 
What brand of rifle is it? When you say it isn't cycling what do you mean exactly? Does the carrier move at all? Is it short stroking? How far is it extracting? Enough to stovepipe? Or is it not extracting enough to eject at all and is rechambering the empty shell.

Changing the buffer and spring might not be a bad idea, just to ensure the correct parts are in place. Don't put a carbine buffer in a rifle unless you use the correct receiver extension and recoil spring. Don't mix and match parts.

If the gas block is clean and aligned with the gas port, the gas tube is new and installed properly, the gas key is installed properly and not leaking, that leaves only a few more things.
 
What exactly is it or isn't doing? You have to be more specific. Stick with the standard basic parts before you start changing things out. If you have a standard buffer in it you are GTG there. The rifle should also function just fine with a standard BCG.
Some over looked problems are loose castle nuts on the receiver extension, loos gas keys, worn bolt lugs, misaligned gas tubes.
What mags are you using?
 
The number one thing that keeps ARs from cycling at range days that I help out is is trying to run the rifle too dry.

Use lube, lots of it. Any excess will blow out in the first couple of rounds.

BSW
 
a bit more information would be helpful, what happens when it doesnt 'cycle fully".. failure to eject? failure to extract? is it short stroking (which would lead to an failure to eject) id like to know more about the nature of the malfunction
 
oldschool45 said:
Would going to a carbine weight buffer help even at the cost of a little recoil and wear.
Click to expand...

If it has a fixed stock wth the rifle length buffer, DO NOT use a carbine buffer!

The carbine buffer is shorter and would allow the carrier to travel too far back, then the gas key will hit the buffer tube and cause some serious damage.
 
my guess is the previous owner probably never cleaned the gas block out and it has enough built up carbine to restrict enough gas flow to short-stroke it
 
What's the brand? Or is it someone's garage build.

Potential issues i suspect (with a recently replaced complete bcg, as OP claims) would be:
Foreign object/excess fouling in gas block
Incorrectly pinned front sight block or gas port misalignment
Damaged or out of spec gas tube (look for kinks, or check for burring where it imserts into the gas key)
Loose or damaged buffer tube

I wouldnt suspect bcg fouling as the major issue if it has a new bcg. But ensure it's lubed right. Also check inside the receiver for unusual signs of wear.
 
My guess is that the gas tube is fouled or port too small. Or possibly it has the wrong buffer spring. I assume you have tried lubing it really well.
I had a similair problem with a Dissapator type, rifle length gas system with 18 inch barrel. The dwell from the gas port to the end of the barrel was to short to cycle the action unless you used NATO ammo. It would be like an under gassed gun. But I have also found that an aftermarket heavy spring can do that as well. Just some thoughts.
 
my guess is the previous owner probably never cleaned the gas block out and it has enough built up carbine to restrict enough gas flow to short-stroke it
Click to expand...

How exactly would you 'clean the gas block out'?

BSW
 
Lol, Brian. Glad to see you posting here as you probably know about AR's than any of the rest of us put together.
 
You might want to travel over to that "other" forum that is pure AR15... they'll have all the information you would ever want and likely some good suggestions. Everyone is telling you to mess with your bolt and BCG parts, yet you said your 'smith put a new BCG in the rifle. I doubt the problem is in your BCG. Yep, it could be a gas issue, but I have never, in years of shooting them, cleaned (or had to clean) a gas block. Like I said, head over to AR15 and see what they have to suggest... that's my suggestion!
 
RainDodger said:
You might want to travel over to that "other" forum that is pure AR15... they'll have all the information you would ever want and likely some good suggestions. Everyone is telling you to mess with your bolt and BCG parts, yet you said your 'smith put a new BCG in the rifle. I doubt the problem is in your BCG. Yep, it could be a gas issue, but I have never, in years of shooting them, cleaned (or had to clean) a gas block. Like I said, head over to AR15 and see what they have to suggest... that's my suggestion!
Click to expand...
except they have some incredibly lame rule about not allowing free email servers when you sign up
 
yeah and they are not getting my for real e mail either....

So far the advice you have been given is good. AR's like to run wet. Some ammo will not reliably function the action. PMC is one I've had trouble with in my WOP match uppers. Never tried the wolf stuff. You say you got the rifle cheap from a pawn shop. There are some cheap AR’s out there that are not Spec anything. I’ve seen some uppers that looked OK but simply would not run because they were out of spec. Your gun smith changed the BCG and had 15 rounds in a row shoot fine. I would find out what ammo he was using and use that.
 
How exactly would you 'clean the gas block out'?

BSW
Click to expand...

with pipe cleaners and solvent
Click to expand...

No, just no.
1) The gas block isn't prone to getting clogged as the hole in the gas block is oversized, compared to the gas port in the barrel. It's also purged by 10,000psi hot gas blowing into it every shot.
2) The gas tube keeps the rest of the gas block relatively clean, because it goes past the gas port and is the corner that the gas flow turns to be directed back to the BCG.
3) It's possible (but very unlikely, with modern ammo) to get a clogged gas tube. The fix is to replace the gas tube. Pipe cleaners and solvent aren't going to do anything if you actually have a clogged tube. You're much more likely to lose the pipe cleaner in the gas tube.
4) It's rare to get a clogged gas system. Possible if shooting a lot of .22 LR using a sub caliber kit and having lead and wax plug the gas port. But even then the fix (if firing full power 556 NATO doesn't fix it) is to remove the gas tube and FSB and remove the plug and/or replace the gas tube.

BSW
 
Ok, this is an Eagle Arms AR15A2; 20" barrel (Rifle non-adjustable stock) the upper and lower are possibly the tightest I've ever seen on an AR. The gas rings in the BCG are in good condition. The rifle was extremely dry on it first run when it wouldn't cycle. I've never limp wristed a pistol but that is how I would describe the intermittent cycling I'm seeing now. When we shoot it and it doesn't cycle I can't tell if the BCG isn't coming back at all or just isn't coming back far enough to chamber the next round and is riding on top of the next round. Next I'm going to try drowning the BCG in lube.
 
Start your troubleshooting from the beginning- place a single round in a magazine, load it into the rifle and fire it. Does the empty extract & eject? Does the bolt lock back?

Also, give a clear and detailed description of the malfunction. Without a description, there is no way too know what's going on
 
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