BCG does not go fully into upper reciever

[amnmmm]

I just finished a .308 build. I cannot close my upper and lower receiver because the BCG sticks out a bit from the upper.

Can someone tell me why the BCG isn't going in completely?

[SmokinXds]

gas tube too long or locking lug interference?

Did you build the upper yourself?

(stupid question sorry, but did you give the end of the BGC a tap to make sure it is seating all the way in?) Might just a tight latch on the charging handle keeping it from seating all the way.

Without more details IDK, maybe your gas tube is to long?
Possibly the lugs on the bolt face aren't lining up or the tolerance is to tight.

Could you check the fit between the bolt and the locking lugs by hand? (With the bolt only, not the full BCG)

If the bolt engages the locking lugs correctly, maybe try installing the carrier with out the bolt, to see if it hangs up on the gas tube.


I'll admit right now that I don't know if this will work but seems like an easy check.

[amnmmm]

I took your advice and removed the bolt. The BC was still sticking out of the upper receiver. The gas tube was too long.

My build calls for a mid-length tube. The tube I ordered was 12 inches long which, if I am not mistaken, makes it a rifle length tube.

SmokinXds, Thank you very much for your advice.

[SmokinXds]

Sweet! I'm glad you got it figured out, and glad I could help.

Happy shooting!

ETA: I believe a rifle length gas tube is somewhere around 15"+, with a middy @ 11.75. Maybe you just ended up with a mid length tube that is out of spec?
If you have a tubing cutter, maybe shave off a 1/4", and see if that works.

[ar15barrels]

I took your advice and removed the bolt. The BC was still sticking out of the upper receiver. The gas tube was too long.

My build calls for a mid-length tube. The tube I ordered was 12 inches long which, if I am not mistaken, makes it a rifle length tube.

Is your build an AR-10 or an LR-308 build?
The gas tubes are about 3/16" difference in length.
If you used an AR-10 gas tube on an LR-308 spec barrel, the gas tube would be too long and you would have the problem you described.

A Midlength AR-15 gas tube should be about 11.8" long.
A Rifle length AR-15 gas tube should be about 15.2" long.
LR-308's use AR-15 gas tubes with some extra bend put into the gas tube.
A midlength AR-10 gas tube should be about 12" long.

[SmokinXds]

Is your build an AR-10 or an LR-308 build?
The gas tubes are about 3/16" difference in length.
If you used an AR-10 gas tube on an LR-308 spec barrel, the gas tube would be too long and you would have the problem you described.

A Midlength AR-15 gas tube should be about 11.8" long.
A Rifle length AR-15 gas tube should be about 15.2" long.
LR-308's use AR-15 gas tubes with some extra bend put into the gas tube.
A midlength AR-10 gas tube should be about 12" long.

This is awesome info right here.
It never even occurred to me that there is a difference between the LAR .308 and the Armalite. I was just going off of the AR 15 gas tube lengths.

This is great timing for me, since I've been looking to build a .308 myself.
One less thing to try and figure out...

[xsefan]

Yeah I have an ar 15 gas tube in my lr 308. Runs great.