Ar 15 probs...

T

Trampstamp

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Apr 21, 2023
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So. After tons of searching I can't really find a definitive answer online (probably because of how Google works).


Latest build is:
.223 18 inch bull barrel with rifle length gas tube
Carbine buffer tube/spring/weight.

No adjustable gas block

Gas block is properly centered verified via carbon ring and the barrel is dimpled so no way to scree that up


Problem:

Initially the gun would fail to eject, wouldn't cycle at all. Empty case still in chamber.

Removed 2/3 buffer weight and it would open enough to stovepipe the spent round. Still not resetting the trigger.

Didn't have a different spring so I (don't flame me lol) cut an inch and a half off the spring. Now it will eject, reset the trigger, pick up a fresh round, and then fail to return to battery.




I'm only on my second ar and the 1st one was easy peasy but also a carbine gas system. I BELIEVE that I need a softer, longer spring such as a rifle length buffer/tube/spring setup. Is that correct?

And... is there a rifle length setup out there that would allow me to keep my adjustable stock? I see the vltor but I don't really know for sure if that will work as it seems to be a "intermediate" not quite rifle length and uses some proprietary buffer weight .
 
20230423_102005.jpg 20230423_102005.jpg 20230423_102054.jpg


So I tore down just in case and I found this scratch? Also found the BCG cotter pin was not in really all the way. Could that drag cause the above issues ?
 
Possibly, though to be dragging THAT much, you would think the charging handle would bind up solid when initially chambering the first round.

Only way to be sure is shoot it again. I suspect you still have a gas problem, maybe some manufacturing debris left in the tube, key, or block?

Might check the bolt piston rings too. A broken or missing ring could cause delayed unlocking.
 
What is the mess inside the upper?

Step 1, clean it. Other than where anodizing has worn, should be original finish on the inside. check for burrs and gouging.
Step 2, What you are describing is most always gas related. Ensure barrel has gas port, gas block is not blocked, gas tube is not damaged and the carrier/bolt tavel and lock without binding. It should go into battery with no round in the chamber under the weight of the carrier/bolt when dropped verticle into the upper. Also check the gas rings on the bolt to ensure aren't worn, broken, properly staggered. Gas rings sould have enough tension to hold the weight of the carrier when placed on a flat surface bolt face down and in the unlocked position. Again, clean of debri and lubed.
Step 3, run it wet. AR's like to be well lubed.
 
ID-shooting said:
What is the mess inside the upper?

Step 1, clean it. Other than where anodizing has worn, should be original finish on the inside. check for burrs and gouging.
Step 2, What you are describing is most always gas related. Ensure barrel has gas port, gas block is not blocked, gas tube is not damaged and the carrier/bolt tavel and lock without binding. It should go into battery with no round in the chamber under the weight of the carrier/bolt when dropped verticle into the upper. Also check the gas rings on the bolt to ensure aren't worn, broken, properly staggered. Gas rings sould have enough tension to hold the weight of the carrier when placed on a flat surface bolt face down and in the unlocked position. Again, clean of debri and lubed.
Step 3, run it wet. AR's like to be well lubed.
Click to expand...
The mess is materials worn during initial firing and a ****load of oil, as AR like to be lubed .

It goes into battery fine if manually charged. Well, before the spring was cut. Gas port is certainly flowing. I don't see much evidence that gas Is getting through the tube and I suppose I shouldn't dismis the possibility that could be blocked from the factory
 
js8588 said:
Being smaller than the port in the gb is normal. The gas port on the barrel should be ~.090-.095.

What ammo were you shooting?
Click to expand...
Tried winchester 55gr fmj garbage, and some better 62gr varmint ammo (don't know what it was. Was commercial ammo with fresh brass) someone else had at the range. No change In operation.
 
Thoroughly cleaned and oiled. Confirmed once more that BCG travels freely.



I have a suspicion that the groove was carved by the bolt pin dragging because perhaps the bolt carrier wasn't moving due to being up against a hard carbine spring and the blowback of the cartridge pressing the bolt into the BCG causing that pin to try and rotate into lockup? I might have sniffed too much solvent ‍️
 
Verify that the gas tube is proper length. I have seen a couple posts where they were a faction of an inch too short and that causes all kinds of problems. With the tube off of the barrel blow through the tube to make sure it’s not blocked. Next step is to put the gas block and tube back on, then take the bolt out of the carrier and watch to make sure that the tube and gas key line up properly. A slightly off center hole in a barrel nut can push a tube off center and cause issues.
 
Hmmmm. I'm going to swap onto another carbine lower and try that. I recall that this buffer kit seemed like it was opened before I bought it. Like maybe someone had problems and returned at any rate I'm going to swap this upper onto another carbine lower. Go from there
 
Trampstamp said:
Hmmmm. I'm going to swap onto another carbine lower and try that. I recall that this buffer kit seemed like it was opened before I bought it. Like maybe someone had problems and returned at any rate I'm going to swap this upper onto another carbine lower. Go from there
Click to expand...
Good idea, but I would try swapping the BCG first.
 
You have to start at the beginning.
What is the gas port size?

As already stated it needs to be around 0.099" , Crane spec is 0.0995" for an 18" barrel.
My 18" Wilson Combat has a 0.0995" gas port and cycles nice with a Vltor A5 with rifle spring and A5H2 (5.3oz) buffer.
Recently swapped that out for an A2 which is basically the same thing, rifle spring and 5oz buffer.
A carbine extension with a spinco blue spring and H2 buffer would work also.
A regular carbine buffer and spring would be pretty snappy.

0.0995" is a #39 drill bit, about $10 for a good one.
Once the gas port size is established you can move on down the line to see where the gas is leaking off.
 
Trampstamp said:
Tried winchester 55gr fmj garbage, and some better 62gr varmint ammo (don't know what it was. Was commercial ammo with fresh brass) someone else had at the range. No change In operation.
Click to expand...
I'd also try some mil spec 556 m193. IMI is good stuff. Of course, I'd have done that before clipping the buffer spring.
This ammo.
https://www.midwayusa.com/product/2090862857?pid=898842

And while you're at it, grab this buffer spring.
https://www.midwayusa.com/product/1025175081?pid=233281
 
Because of geography and travel time I wasn't able to get back to my other guns but I did have an hour here to mess with things and I put the spring back together (janky) with all the same parts as before and did manage to get a few rounds to cycle properly before the spring unstained itself.



Yes I know none of that no sense is right but I'm in the field so to speak and improvising.



Evidence so far suggests that I should have broke down, cleaned, inspected, and made that adjustment to the cotter pin last night and I'd be shooting happy right now on the carbine buffer. So... I'll grab the recommended spring above and give it a go. Thanks guys I'll follow up lol
 
I just went through an issue with my AR... I was getting stovepipes, which is the exact opposite of what you are getting. Either you are binding up somewhere, or it's not getting the right amount of gas. Although unlikely, if you have a pipecleaner, run it through the gas key to make sure there isn't a chunk of something stuck in there, too.

FWIW, even with a rifle-length gas system, you should be able to use a carbine tube/buffer/spring. You may have to dink with the buffer weight, or at the outside maybe the spring... but nothing drastic.
 
Charlie98 said:
I just went through an issue with my AR... I was getting stovepipes, which is the exact opposite of what you are getting. Either you are binding up somewhere, or it's not getting the right amount of gas. Although unlikely, if you have a pipecleaner, ...
Click to expand...


I found my pipe cleaners. Right in my smoking pouch. And then I decided that having a delicious bowl of boston stoker tobacco was much more appealing than further dicking with this gun today I'll get back into it once I've returned to civilization and just go test it at the range close to home... oh and of course I'll toss a pipe cleaner through the gas key to make sure there's no gremlins in there.
 
sevt_chevelle said:
A vltor buffer system, while nice, isn't gonna magically solve your problems.
Click to expand...
I'm not asking it to solve a gas problem. I am asking it to not be a 50 dollar buffer and spring kit . I don't have much faith that I have a quality bugger setup and I don't really want to stuff money into a 20 dollar tube and the fact is, I need a spring at the very least.






That aside, I have to believe that one of three things happened


1: some stuff was in the barrel, gas block or key left from milling, and, it's been cleaned out now.

2: that cotter pin was dragging and causing Holy hell

3: El cheapo buffer spring was stiff as a board and not allowing any cycling to occur. Hence after I shortened it I had a different issue.

1st problem was bolt carrier was short stroking/not ejecting . After the hillbilly spring mod, the current issue is that the action cycles, ejects, picks up a round, resets the trigger,and just can't drive it home to lockup.
 
Last edited by a moderator:
Never mind the 0.0995" gas port spec, that's for a 5.56 NATO or .223 Wylde.
I imagine it would have to be a bit larger for a .223 chamber being lower pressured ammo.
Speaking of .223 chambers, you may want to watch what you are feeding it.

Why did you pick that barrel?
.223 chamber with a 1:9 twist seems like it's geared towards 55gr varmint loads.
 
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