Hello all,

I purchased a sig 556 pistol lenth upper receiver and have SBR'd it already. Problem is that one of the nutsert style lugs that the upper optics rail attaches to has spun out and split from the rest of the receiver (see photo). I already scuffed the metal and tried various epoxies but nothing will hold up to even minor shock.

Does anyone have any ideas on how to fix short of TIG welding it on and then refinishing? I've looked around for parts and can't seem to find anything similar. The photo of the inside of the receiver is on another upper that is proper.

That's some bullshit, that should not break that way.

You might try contacting SIG, see what they say about sending it in for some kind of warranty type repair? Shot in the dark, but couldn't hurt.

Not being intimately familiar with the SIG's innards, I'm assuming a bolt carrier rides under that, with very little clearance?

If so, I can't see any other way than welding it, unless some sort of external mount is an option.

Even so, I wouldn't want that gaping hole up there.

Correct. The bolt carrier rides right under that. I was hoping (based on the hex visible underneath) that it was a replaceable part versus a welded on one.

And ya idk what caused it to happen since I bought it this way.