Yet another barrel cluster!

[OneGuy67]

I bought another barrel off of Gunbroker and upon receiving it on Monday, I see two holes in the barrel extension, directly across from each other. It is a Green Mountain barrel that I bought off a third party seller. Wen I called Green Mountain barrel today, I had to leave a message that they have not yet returned.

What the heck are the holes for? Is it safe to mount and fire?

Before anyone says "Take it to Bert", know that I have already consulted with the firearm magician extraordinaire (and I say that with all seriousness as he is great!) and he does not know either.

33229

Any thoughts?

[cofi]

Looks like this
http://www.ar15.com/archive/topic.html?b=3&f=12&t=608846

[BPTactical]

My intital thought was vents for overpressure in case of a casehead separation or primer blowout.
Makes perfect sense.
Except for one small problem-the holes would be blocked by the receiver ring so the gases aren't going anywhere.

In reading the linkage that Ian kindly provided it seems to me it cures a rarely occurring issue. Imagine the fun one would have if the pin worked loose.
Fun to clean as well.

[J]

Its likely a Sig Extra, as stated in that thread. They put some assist pins in a generation of their M400 that need the holes in the extension.

[OneGuy67]

I spoke with someone from Green Mountain barrels and he stated it was a barrel produced for Sig with a extractor rest. He believed it wouldn't be an issue to mount the barrel on a standard AR with the holes. He says they sold thousands of barrels just like that to people and haven't heard of an issue.

I dunno. I am worried that those holes cause a weak spot somehow.

In any case, the seller on gunbroker has gone all retard on me and won't take a return on the barrel. So, I guess I am stuck with it.

[Delfuego]

They're "Speed Holes"


http://www.youtube.com/watch?v=XVV_COOey0E

Beware of Gun Broker, I hope it all works out.

[BPTactical]

Considering that the barrel is fully supported in its circumference by the receiver strength should not be a concern. You still have full lock up of the bolt lugs in the extension.
My only reservation would be the holes would be collection points for debris.

Run it.