AR short stroke, things to check?

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So my AR is short stroking to due to gas issues*.

Going to change the gas rings, anything else I should look for? Could it be a buffer issue? Maybe I over oiled it and now I have gunk buildup? Did Hillary's operatives sabotage me with AR Ebola? Is there a better way to clean the gas tube other than pipe cleaners?

Any advice and double entantres welcome.

*Complete Factory Bushmaster, (Wyndhm, circa 2010). 14.5" w 1.5" brake). Mid power reloads cycle action fully only half the time, other half cycles action ~1/2. Factory ammo cycles, but last round won't lock bolt open. Happens with multiple magazines. Does not happen with other AR (20" franken AR). Ammo described above always has cycled reliably (~99% w/ reloads 100% w factory) over last 4 years. First time firing after having been cleaned, the left in safe for 3 months. Worked for about 20 rounds, then started acting stupid. Manual mechanical operation reveals no issues
 
Gas rings first.

After that you need to look at:

Is your buffer and spring lubed lightly?

Is your BCG wet?

Buffer weight. Is it too heavy?

Buffer spring pin - Some buffers use a pin to keep the end in place (and the weights inside) I've seen two back out and drag inside the buffer tube.

Charging Handle (Is it straight?? They can and will bend if it's a shitty quality one)

Gas tube - Is it straight and does the BCG go into battery with low effort? I've seen the gas tube be bent inside the upper, causing drag inside the gas key and sometimes bad enough to prevent the gun from going into battery reliably.

Gas block properly aligned over barrel gas port?

Roll pin missing from gas tube/gas block? This will allow too much gas to escape at the gas block. This would be noticeable if you fired the rifle with the hand guard off.

Barrel Gas Port - Is the gas port undersized? This will restrict volume of flow.

Check those and get back to us.
 
Xtry51's got it covered. I'll add some noise anyway.
My 16" mid length gas upper started to whimpy cycle.
Turns out, the low profile gas block came slightly loose and rotated slightly (barely noticeable).
This effectively reduced the size of the gas port. Straightened the block and tightened and it's been 100% with all ammo.
 
So you cleaned it put it away and now it doesn't work?
Possible something got where it should have not? Piece of cleaning patch. Some gunk in the gas key?
I would just clean it again check everything and give it a light lube of clp.

If I understand you.... the lower works with a 20" upper, correct. If so the buffer should be fine for a carbine length gas system.....Possible it's to light? You say it worked before you cleaned it. Really need to check where you touched it.
I would closely inspect the BCG make sure gas key is tight and make sure your bolt is clean and seals are free.

I'm just digging into ARs but so far only short stroking I have seen is loose keys, heavy crud down through the key into bolt and one loose gas tube. Front gas tube retaining pin was missing gas tube was just floating around. Tube and gas key beat up.

I built a upper with a " bargain" LPK the bolt catch was shit.
 
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I was having the same issues with a gun I bought used a year or so back. Found out that the BCG on a gun I bought used was the culprit. The inside of it was so carbon fouled that the gas rings werent sealing well and it wouldnt seat fully. Bought a cleaner tool and havent had an issue since I scraped it clean.
 
If it was working before, then its probably not the buffer weight or anything that hasn't changed. I would do a full inspection for debris and gunk. Gas key, rings, gas block and tube. Maybe a piece of pipe cleaner got stuck in there and is restricting flow.
 
Make sure you have a carbine length buffer spring not rifle length. I had this problem with a bought-used AR-15.
 
If you have access to another bolt carrier group, I'd swap it out for a few shots of factory ammo. If it fixes it, then you can begin troubleshooting the original one.

I don't think its the wrong spring or buffer for 2 reasons,
1) it used to work
2) its a factory rifle.

But then again, it takes 30 seconds to check.


Max and min freelength
Rifle is 11 3/4 Inches to 13 1./2 inches
Carbine is 10 1/16 inches 11 1/4 inches

Don
 
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Don't worry about the gas rings lining up. That is an old myth that will not ****ing die. They compress and the gaps are almost not existent. Just like a ring on a piston in a motor.

For gas ring wear
Per TM 9-1005-319-23&P.

4. Check bolt assembly (5) for proper fit with bolt
cam pin removed. Turn key and bolt carrier
assembly (6) and suspend so the bolt assembly
is pointed down.

NOTE:
The bolt assembly must not drop out. If
weight of bolt assembly allows it to drop out
of key and bolt carrier assembly, replace bolt
rings (p 3-21).

 
So my AR is short stroking to due to gas issues*.

Going to change the gas rings, anything else I should look for? Could it be a buffer issue? Maybe I over oiled it and now I have gunk buildup? Did Hillary's operatives sabotage me with AR Ebola? Is there a better way to clean the gas tube other than pipe cleaners?

First do a detail clean, and go easy on the re-lube. You already did the gas rings, so that's that.

Could be a buffer issue, though I doubt it if it's a carbine buffer and a stock spring you're likely fine there. Something to check though, before drastic measures.

If I had to guess, I'd say you're under-gassed. Could be fouling in the gas tube, but more likely your gas block isn't aligned. If the gas block is slightly misaligned, you could be blocking half the gas port in the barrel and robbing the system of cycling pressure. I've also heard of people getting factory guns that for some reason had an under-sized gas port that simply needed to be opened up.

Has this gun worked fine in the past? If so, It's probably not the port diameter. How is the gas block or FSB attached to the barrel? I would wonder if you might have bumped the front sight and caused the block to rotate slightly off center. Cross-pins under the FSB would make it hard for this to happen, but set screws can back out or just run along the barrel.
 
How worn did the gas rings look...... I forgot to snap pictures but I just help my friend rebuild his bolt.
Had about 4k rounds through a budget upper build . The bolt lost a lug. When I took the bolt appart after we went to the range I found only 2 rings and one was basically only staying in by friction. Fell off in 2 pieces.
The gun gets abused and is basically a mag dump gun with a bump fire stock. I was actually shocked how well it ran as beat up and as dry he runs it...
 
It is amazing sometimes. I have a $269 with BCG and CH upper from PSA on my M16 lower. It runs like a champ. Its only got about 2000 rounds through it, but they have come in 30 to 100 round bursts. (I love it that a $269 upper can get so hot you can smell the oil burning off of it, but it still runs)

Do
 
some of the PSA uppers with FN barrels are some of the best on the market for any price. As long as you stick with one that is using a CHF FN made barrel you are getting quality. Not taking away from any other brand but anyone who believes PSA is all crap has no clue what they are talking about.
 
some of the PSA uppers with FN barrels are some of the best on the market for any price. As long as you stick with one that is using a CHF FN made barrel you are getting quality. Not taking away from any other brand but anyone who believes PSA is all crap has no clue what they are talking about.

I won't say they are Crap but I will say I have a funny feeling PSA buys FNs factory 2nds or Contract rejects. My buddy has one FN barrel the "machine gun steel with heavy chrome" just looking down the barrel you can see how "rounded" the grooves and lands are from the heavy chrome. He also called and said he thinks the chrome is flaking ?

That said PSA offers some stuff that is hard to beat for the price....
 
Excellent.

How would you describe how the bolt moved with the old gas rings. Was it sloppy loose?

Be it true or not the ret USMC armor at my club said the gas rings are toast if the bolt falls forward from its own weight when held straight downHe also said some people over look the BCG also. He says the BCG will most likely crack vs wearing wear the bolt rides.
His first question when anyone asks him about a gun problem. 1. Did you clean it and or what did you touch last.
 
We got a batch of bcg in the shop last fall with loose gas keys. 6 out of ten were loose. The staking was a joke, and the manufacturer sucked balls when we called them on it.


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I never had Gas ring wear to that point but I figure after 2k rounds ill just replace for pre maintenance.I get them at BCM for like 3 bucks. I have had issues with PSA BCG's . some work some don't. I had them with bad tool marks and one that wouldn't go into battery. But then I had one that went around 2200 rds with zero issues. I no longer use PSA BCG's. I'm sure they are just fine but for 10-20 bucks more you can do better.
 
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I never had Gas ring wear to that point but I figure after 2k rounds ill just replace for pre maintenance.I get them at BCM for like 3 bucks. I have had issues with PSA BCG's . some work some don't. I had them with bad tool marks and one that wouldn't go into battery. But then I had one that went around 2200 rds with zero issues. I no longer use PSA BCG's. I'm sure they are just fine but for 10-20 bucks more you can do better.

I have had 3 different PSA BCGs. One had to be broken down completely and cleaned before it would function properly. One was and still is perfect but the 3rd was only ok.....it is Nib coated....not impressed with that one....the finish stained after the first outing....it functions ok but the finish is only so-so.

The FN barrels I've had or have are all top notch. I highly doubt they are selling them with the FN name as seconds or rejects. there are defects from every manufacturer and I am sure the FN barrel mentioned mentioned above would be quickly taken care of.

my nephew had a bravo company barrel who's head space was so tight it was laughable. Not even close. It had a round stuck on his first outing. They made it right but it shows that there are bound to be defects with any manufacturer every now and again. I am not Knocking Bravo in any way shape or form but things happen.
 
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One of my Aim Surplus BCGs (the ones with the loose gas keys) now has about 1000 rounds and the bolt slides a bit too freely. The rings aren't worn, but there is certainly much less ring tension than when new.

The gun still runs fine and the ejection pattern has not changed. Its a "toy" gun, so I'm going to continue to use it. Strange though.

Don
 
One of my Aim Surplus BCGs (the ones with the loose gas keys) now has about 1000 rounds and the bolt slides a bit too freely. The rings aren't worn, but there is certainly much less ring tension than when new.

The gun still runs fine and the ejection pattern has not changed. Its a "toy" gun, so I'm going to continue to use it. Strange though.

Don
My NIB X from Aim is still perfect and will stand up still on its own. try new Gas rings for fun to see. I get them at BCM for like 3 bucks.
 
I have had 3 different PSA BCGs. One had to be broken down completely and cleaned before it would function properly. One was and still is perfect but the 3rd was only ok.....it is Nib coated....not impressed with that one....the finish stained after the first outing....it functions ok but the finish is only so-so.

The FN barrels I've had or have are all top notch. I highly doubt they are selling them with the FN name as seconds or rejects. there are defects from every manufacturer and I am sure the FN barrel mentioned mentioned above would be quickly taken care of.

my nephew had a bravo company barrel who's head space was so tight it was laughable. Not even close. It had a round stuck on his first outing. They made it right but it shows that there are bound to be defects with any manufacturer every now and again. I am not Knocking Bravo in any way shape or form but things happen.

you should always do a detailed strip and clean of almost all guns/parts they are generally slathered in a rust inhibitor of some type that is far from lube.
 
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