What is this silver piece for?


It fell out as I was cleaning my AUG, now I don't know what to do with it.




I thought it went into the chamber area because it fits, but when I assemble the AUG, it falls out.




There's no video on YouTube with an answer. Is this a full auto specific part?




Thanks







 

That's the steel receiver bushing where the bolt thrust pieces ride. I would suggest you call Pete Athens.

Where does it go? Is it broken?

It goes into the receiver where the bolt thrust pieces (the chromed rods that hold the recoil springs and anti-bounce weights inside) ride. There are two in the rear and one up front. They are crimped into place. I can't tell from your photo whether yours appears broken. It looks from your photo as though the two in the rear are intact, but a higher resolution photo would help. I would definitely recommend calling Pete.

Edited: it looks as though this came out of the right rear thrust piece hole in the receiver.

That helped. That's exactly where it's supposed to go.

Thanks, Josh!

As others have pointed out this is one of the receiver thrust rod bushings, that protects the aluminum receiver from the thrust rods as they actuate back and forth.  It is nothing full auto specific.

The AUG receiver has three stainless receiver bushings, two in the rear of the receiver near the trunnion (and can be seen in  your picture) and a 3rd thrust rod receiver bushing on the right side up near where the thrust rod goes through the receiver and makes contact with the gas block on the barrel.  The analogous hole on the left side of the receiver near where the charging handle is doesn't have a corresponding bushing insert and is left as anodized aluminum.

The two rearward/trunnion located bushings are crimped into the receiver via the bushing being flared outwards on both ends, effectively locking them in place. (Steyr also appears to use some adhesive/Loctite as well)

The bushing up front, closer to the gas port is only flared on one end.  I believe this bushing is primarily held in with some sort of adhesive as well as a small flaring/staking on the opposite side.  

Based off your pic  the bushing only appearing to be flared on one end so my guess is it is the one from up near the gas port.  Its hard to tell if both rear bushing are in place due to the angle of the pic and the oil/carbon deposits.

Assuming it is the front-right gas port location bushing, I would just thoroughly clean and degrease the bushing and the hole in the receiver it is seated into and then bond it back in there with Loctite 638 retaining compound and 7471 primer.  

Hope this helps.