What is this?

[JayFlip]

This was attached to the barrel of an AR that I bought recently. It was between the pins of the A2 gas block. The previous owner has no idea what it is either (he didn't put it there).

For some reason the images uploaded massive sized, so here are imgur links: http://imgur.com/Hvu2G6e http://imgur.com/gTMduEA

 

[H.K.Glock 007]

3 possibilities.
1. Reverse Oscillating foo foo valve.
2. Doo dad madeally doo hicky.
3. Shoosher.

In that order.

 

[dogzilla]

How can you not know what that is? It's a doohickey

 

[Jäger1]

Sling swivel mount

 

[TV-PressPass]

We have a winner

 

[Greenhorse six]

How can you not know what that is? It's a doohickey

No ya ijiot , that there is a slingama thing.

 

[Shooter1of38]

Slide fire barrel clamp of death.

 

[Outwest1213]

That device allows the firearm to shoot into space.

 

[JayFlip]

Thanks Jäger. I wish all the other answers were true too

 

[enefgee]

You're all wrong - that's what "that shoulder thing that goes up" bolts to.

 

[aiwa]

 

[Skin]

Would never have guessed that based on on first pic....makes sense now I don't like the idea of a sling mount attached to the barrel better off to have a forward rail sling mount