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7/13/2026 3:41:05 PM EDT
I recently built my first AR 15 but have helped a friend build others previously. When attempting to fire it, I took a slow motion video and was able to see that the BCG is not fully retracting when firing therefore getting stuck. It retracts about halfway back in relation to the opening on the side of the upper then goes back forward.
I'm trying to look for ideas of what specifically I can look at to try and remedy the problem. Seems like a gas problem or a mechanical problem with too much spring pressure but this gun came as a full kit from delta team tactical so I don't believe there should be any incompatibilities with the components.

There is a small gap between the barrel lock ring and the main part of the upper ()

Overall, the gunfire is OK. It just won't eject the empty shell or load a new one in without manual intervention.  

Video: https://i.imgur.com/XW7QKW9.mp4

For what it's worth, it's a 350 legend caliber
7/13/2026 3:45:06 PM EDT
[#1]
What spring and buffer combo are you running?
“All things are said already, but since no one is listening, it is always necessary to start again.”
7/13/2026 3:46:09 PM EDT
[#2]
It sounds to me like it's not getting enough gas.
Loose or misaligned gas block?
An armed society is a polite society.
7/13/2026 3:47:09 PM EDT
[#3]
Quote History
Originally Posted By fulautotank:
It sounds to me like it's not getting enough gas.
Loose or misaligned gas block?
View Quote


This.  It ain’t got no gas in it.  
7/13/2026 3:47:50 PM EDT
[#4]
Quote History
Originally Posted By fulautotank:
It sounds to me like it's not getting enough gas.
Loose or misaligned gas block?
View Quote
This, if the gas block is held on the barrel with set screws, good chance it's come loose or not positioned properly to align with the gas port.
7/13/2026 5:51:37 PM EDT
[#5]
https://www.deltateamtactical.com/davidson-defense--avalanche-in--350--16-inch-ar-15--350-legend-phosphate-rifle-sop-build-kit.html

This is the exact kit I ordered. I don't see some of the specifics mentioned there though
7/13/2026 5:52:11 PM EDT
[#6]
Is that easy enough to check by taking off the hand guard?
7/13/2026 5:53:19 PM EDT
[#7]
Quote History
Originally Posted By D_Man:
This, if the gas block is held on the barrel with set screws, good chance it's come loose or not positioned properly to align with the gas port.
View Quote

It does have set screws. I'll have to take a look at that
7/13/2026 6:50:49 PM EDT
[#8]
If you could get the handgard off and take a picture of the gas block we may be able to tell if something is not right.
Also check to make sure it is not loose.
An armed society is a polite society.
7/13/2026 8:07:51 PM EDT
[#9]
Quote History
Originally Posted By fulautotank:
If you could get the handgard off and take a picture of the gas block we may be able to tell if something is not right.
Also check to make sure it is not loose.
View Quote

I got the hand guard off and lo and behold, the roll pin in the gas block is no longer there. It must have come out at some point after putting it together. Gas tube seemed to have been pushed all the way forward so it wasn't building enough pressure against the BCG I guess?

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