Would you build on this barrel?

[polymorpheous]

What would be the purpose of the build?

Is that rust or is it grease on the barrel extension or what? Hard to tell in the pic.

14.5" RECCE

There's no rust.

[utahjeepr]

The chip is almost certainly not an issue. Very, very slight chance that it is enough of a stress riser to weaken that lug. Keep an eye on it and shoot the barrel out. I wouldn't preemptively change the extension, I don't think it's worth the bother.

[AndyLate]

I would be more concerned with why it chipped than the chip itself.

Andy

[trauma]

I'd skip a build with that going on, maybe some other lugs have stress and are ready to give way.....maybe not though.

With how cheap you can get some new barrels, I wouldn't take a chance on it.

[DG23]

I would be more concerned with why it chipped than the chip itself.

Andy

That was my first thought looking at the picture.

Why does everything look so new but that one spot is gone?

[Uncas47]

If you're asking for opinions, I don't like it. It's got a nasty shape to it and the photo appears to show marks on the adjacent lugs. I have no idea what caused that, was it ever installed on a rifle and shot? Any flinch I already have would only get worse every time I dropped the hammer on that.

[OldArmy01]

Yes I would.

If the chip were on the chamber side, I wouldn’t.

[Straight Shooter]

Do you happen to know how that even happened? Not seen that before.

[Esq.]

I would be inclined to send it back to them and say, "Yo, shit's broke". That should never happen (unless the barrel has 89 kajillion rounds on it etc...)... and everyone knows it.

[polymorpheous]

Do you happen to know how that even happened? Not seen that before.

I don’t.
But judging from the face of the extension, and lack of wear from the bolt carrier, I’d say it wasn’t fired much.
The lug next to it to the right also has a little bit of peening. It’s visible in the pic in the OP.