Fixing an AR15 upper

[Tachyon1]

Hello,

I purchased an AR15 .224 Valkyrie upper to go with a lower I made.

When I took it out on the range, I found that it was essentially a single shot. On firing, it locks up hard and fails to extract. Usually, I have to remove the upper and tap on the bolt carrier with a punch and a hammer to extract the case. I did this a couple dozen times, so it's not something that will work out on its own.

The gentleman I purchased the upper from suggested that an adjustable gas key might fix the issue. He offered to fix it, but he was affected by recent fires and so I haven't wanted to bother him. At the same time, no local gunsmiths have been returning my calls, so I'm taking this as a learning opportunity.

My question is simply this: based on what I've described, is there agreement that a new adjustable gas key would fix the issue? Or should I try something else first?

Thanks for any advice.

[ar15barrels]

Not enough info to make any type of diagnosis.

What length barrel and gas system?
What size gas port?
Factory ammo or reloads?

Post some pictures of your fired cases to start.
Could be a chamber problem.
Could be a gas problem.
Could be other problems.

[ozarkpugs@gmail.com]

Something is binding , what does the cartridges look like when you get them out ? If the bcg is working freely and no sign of binding it is probably in the chamber or ammo . Did you clean the chamber good then better? Did you try more than 1 factory load .

Sent from my Moto E (4) using Tapatalk

[wpage]

Give a good cleaning and see if all fasteners are tight.

[dscoduc]

Where are you located?

[Tachyon1]

The barrel is, according to the tag:

"20" 1:7 Cold Hammer Forged Spiral Flute
Adjustable Gas Key
Rifle-length Gas System
Nitride MPI BCG
15" Keymod Rail
Nitride Low-pro Gas Block
Ambi-Charging Handle
Linear Compensator"

I was using American Eagle 75 grain FMJ. There isn't really anything else on the shelves here, so I hadn't tested other factory ammo.

The fired brass has scratches on the body of the case towards the head; it's unscratched from the neck to about the middle. I don't have a web location yet to post photos.

It was brand new when I tested it. I cleaned it at the range to try to fix, but I can do a more thorough job. Though, I don't think I want the rifle to be so finicky about dirt for proper extraction.

I'm in Northern CA.

[ar15barrels]

The barrel is, according to the tag:

"20" 1:7 Cold Hammer Forged Spiral Flute
Adjustable Gas Key
Rifle-length Gas System

What's the gas port diameter?

[divingin]

I'm in Northern CA.

Off topic: Northern California is a pretty large area. The question about your location was posted to see if someone on here was close enough to assist you in person. A more accurate location may get you more help.

[God Bless America]

I don't have a web location yet to post photos.

Upload from your phone.

[Scota4570]

"On firing, it locks up hard and fails to extract." "Usually, I have to remove the upper and tap on the bolt carrier with a punch and a hammer to extract the case"

Factory ammo? Sounds like a rough/bad chamber? You should not have to drive the fired cases out. IF the chamber was good you could easily extract them with the charging handle.

[K001]

QQ - Are you firing .223 or .224 Valkyrie ammo and have you verified the barrel is chambered for .224 Valkyrie and not .223?

[ozarkpugs@gmail.com]

You can't accidentally fire one in the other .

Sent from my Moto E (4) using Tapatalk

[vintagedude88]

Are you using a 5.56 bolt on your .224 barrel? The bolt needs to be for a 6.8 SPC. Check and see if you have the proper bolt for the barrel extension.

[ar15barrels]

Are you using a 5.56 bolt on your .224 barrel? The bolt needs to be for a 6.8 SPC. Check and see if you have the proper bolt for the barrel extension.

[kelvin232]

Take bcg apart and lube everything. Fixed my problem.