What is this hole in this barrel extension

[ARCHIVED THREAD] - What is this hole in this barrel extension

Posted: 11/21/2014 8:56:11 PM EDT

asked in pistol forum, but I need to know wtf is this, pin pressed into wall of extension opposite the hole Is this right? I don't recall seeing anything like this, hole measures 0.190"

Posted: 11/21/2014 8:58:34 PM EDT

[#1]

Quoted:
http://www.ar15.com/media/viewFile.html?i=70517
asked in pistol forum, but I need to know wtf is this, pin pressed into wall of extension opposite the hole Is this right? I don't recall seeing anything like this, hole measures 0.190"

View Quote

Looks like it would prevent the bolt from locking in place. Something to disable the rifle/barrel?

Posted: 11/21/2014 8:59:51 PM EDT

[#2]

well that's a bit fucked up, as I just bought this for a pistol build.

Posted: 11/21/2014 9:00:20 PM EDT

[#3]

Maybe this support pin

Posted: 11/21/2014 9:01:57 PM EDT

[#4]

Quote History

Quoted:
well that's a bit fucked up, as I just bought this for a pistol build.

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Have you tried fitting a bolt? I was just guessing.

Posted: 11/21/2014 9:03:28 PM EDT

[#5]

I should add this is a 7.5" barrel

Posted: 11/21/2014 9:03:49 PM EDT

[#6]

I can try a bolt right now

Posted: 11/21/2014 9:03:55 PM EDT

[#7]

Sig barrel?

Posted: 11/21/2014 9:04:34 PM EDT

[#8]

Quote History

Quoted:
Maybe this support pin

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Interesting, never heard of such a thing.

OP's barrel does look like that though...

Posted: 11/21/2014 9:06:08 PM EDT

[#9]

Quote History

Quoted:
Sig barrel?

View Quote

I'm going with this.

Posted: 11/21/2014 9:07:33 PM EDT

[#10]

it's from Green Mountain Rifle Barrels, and the extractor lug only will turn over that pin, so I guess that's right?

Posted: 11/21/2014 9:09:08 PM EDT

[#11]

The reason for the hole is so that upon machining for the pin a shouldered hole can be made; the pin has a step to control its protrusion. As for the purpose of the pin itself, I'm currently at a loss.

Posted: 11/21/2014 9:10:03 PM EDT

[#12]

now that I'm going back and looking at the website, it clearly shows it too. It keeps the extractor from getting too loose too fast on an overgassed system apparently

Posted: 11/21/2014 9:10:10 PM EDT

[#13]

Well that's cool I guess.

I built a rifle with one of their barrels recently, couldn't be happier btw, and I didn't get an extractor support pin.

Not sure if I'm jealous, but I wonder if it was a production over run.

Posted: 11/21/2014 9:10:33 PM EDT

[#14]

Quote History

Quoted:
it's from Green Mountain Rifle Barrels, and the extractor lug only will turn over that pin, so I guess that's right?

View Quote

I was just about to guess it was a GMR.

I have the exact same 7.5" barrel, same hole. I found no answer anywhere, and tried the same threads in GD, pistol, build etc. No one knows.

I just built it and shot it. It works.

ETA: After reading thread, I am still intrigued, and have even MORE questions than I did before. Im gonna go read more.

Posted: 11/21/2014 9:12:18 PM EDT

[#15]

Quote History

Quoted:
The reason for the hole is so that upon machining for the pin a shouldered hole can be made; the pin has a step to control its protrusion. As for the purpose of the pin itself, I'm currently at a loss.

View Quote

I guess it helps with extraction somehow.

Posted: 11/21/2014 9:13:06 PM EDT

[#16]

yeah I'm gonna try it, my third barrel from GMR

Posted: 11/21/2014 9:14:21 PM EDT

[#17]

The other thread says that the pin is to support the extractor during the higher unlock speed due to a short gassed barrel. It keeps the extractor from losing its grip on the case rim while it is in the chamber. I'd guess that you'd only see it on super short barrels.

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Posted: 11/21/2014 9:16:15 PM EDT

[#18]

Did you pound it on the ground? The end looks banged up a bit.

Posted: 11/21/2014 9:19:00 PM EDT

[#19]

i did drop it about two and a half feet onto vinyl tile but that all wiped off no dings. I'm off to mount it

Posted: 11/21/2014 9:33:57 PM EDT

[#20]

Quote History

Quoted:
i did drop it about two and a half feet onto vinyl tile but that all wiped off no dings. I'm off to mount it

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STS! Enjoy!

Posted: 11/21/2014 10:24:07 PM EDT

[#21]

Posted: 11/21/2014 10:32:08 PM EDT

[#22]

Quote History

Quoted:
http://www.ar15.com/media/viewFile.html?i=70522

View Quote

Ugh, I have a headache just looking at it.

Posted: 11/21/2014 10:47:29 PM EDT

[#23]

I suspect it's gonna be that way

AR equivalent of a snubnose?

Posted: 11/26/2014 1:46:40 PM EDT

[#24]

VA, didja get to the range yet? I have one of those barrels on the way, I'm curious how yours shoots.

Posted: 11/29/2014 6:14:16 AM EDT

[#25]

Shoots fine
final assembly here:
http://www.ar15.com/forums/t_1_5/1691431_Black_Friday_ish_new_pistol__Yeah__or_Meh.html

[ARCHIVED THREAD] - What is this hole in this barrel extension

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