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View Full Version : Removing the pin from that barrel trunnion thingie


raubvogel
December 06, 2016, 21:45
I know they do not call it a trunnion in the AR, but I do not know its proper name and it sure seems to fit the role -- hold the barrel, provides the locking lugs for the bolt to lock itself to when closed, and has feed ramps. In any case, I have an used one I want to knock the big locating pin out of it. How to do the deed?

tac-40
December 06, 2016, 22:21
Those locator pins are harder than woodpecker lips. Drilling is pretty much out of the question. The pins are normally pressed into the barrel extension and contact the barrel threads but do nothing to hold the barrel in place. The pin is strictly to index the barrel assembly. You could try to grab the pin in a vise and then force the barrel away from the vise using wedges. This may remove the pin.

One sure way to remove the pin is to separate the barrel extension and barrel. The pin can then be driven through the extension and out of its hole. I have seen torques specs for assembly of the extension and barrel to be between 30 and 150 foot pounds. This means you would need an el supremo barrel vice and a dedicated barrel extension tool.

http://www.joeboboutfitters.com/v/vspfiles/photos/BRN-080-000-637-2.jpg

http://www.northerngunparts.com/images/products/detail/AR15M16BarrelExtensionNutRemovalTool.jpg

raubvogel
December 07, 2016, 06:38
Just to let you know, I have it already out of the barrel, as in (stealing pict from Apex)
https://www.apexgunparts.com/media/catalog/product/cache/1/small_image/228x/9df78eab33525d08d6e5fb8d27136e95/1/4/14nov16_colt-extension-vg_mid01.jpg
What I am trying to figure out is how to get pin out. Padded vice + Hammer + punch time? The angle for the punch looks a bit challenging

MAINER
December 07, 2016, 10:15
If you don't have the means to press it out, then the BFH, padded vice and appropriate size punch would be called for.

Just curious as to why you want to remove the pin in the first place? :confused:

btw; That thing is known to AR enthusiasts as a "Barrel Extension", and you are
therefore attempting to remove the "Barrel Extension Pin". Hope that helps. :)

Looks simple enough, should just be a press fit.
http://www.jsesurplus.com/ar15barrelextensionpinpinonly.aspx

lysanderxiii
December 07, 2016, 10:39
Just to let you know, I have it already out of the barrel, as in (stealing pict from Apex)
https://www.apexgunparts.com/media/catalog/product/cache/1/small_image/228x/9df78eab33525d08d6e5fb8d27136e95/1/4/14nov16_colt-extension-vg_mid01.jpg
What I am trying to figure out is how to get pin out. Padded vice + Hammer + punch time? The angle for the punch looks a bit challenging

Well, if the barrel is out, you could press the pin all the way through, and it will drop on the threaded area....

But, I have to ask, why you need it out? Does it interfere with threading in a new barrel? If it doesn't, I wouldn't worry about it.

L Haney
December 07, 2016, 19:09
But, I have to ask, why you need it out?

This is buggin' the shit outta' me too.

Whazzup?

ETA: But if I wanted it out I'd use a V block, not any kind of vise.

jhend170
December 08, 2016, 09:50
"Barrel extension" is the term you're looking for.

Like the last post, why on earth do you need to remove it? In many cases though it's a blind hole. It's sole purpose is to mark the vertical point in the upper receiver so that it's aligned with the gas hole in the barrel.

If you intend to reuse the extension though it has to be on a barrel that has not had the gas hole drilled yet (or on one that has been welded so that it can be moved). Really not seeing the "why" here for any of it though. Essentially any new barrel with come with the extension already installed, sooooo????

darkest2000
December 09, 2016, 01:16
If you don't even know what a barrel extension is on an AR, you shouldn't **** with that pin.

raubvogel
December 09, 2016, 10:01
If you don't even know what a barrel extension is on an AR, you shouldn't **** with that pin.

I guess I better let you explain what I planned to do with it since being able to name a part is clearly more essential to its operation than knowing its function.

Bug Tussell
December 09, 2016, 10:21
I guess I better let you explain what I planned to do with it since being able to name a part is clearly more essential to its operation than knowing its function.

Don't worry about him. The rest of us are politely awaiting your reasoning regarding the removal of said pin from said AR part. Please to illuminate.

hueyville
December 09, 2016, 15:11
I am baffled as well. Has pin been damaged? Only way I would remove the extension from an AR barrel is if it were improperly indexed with gas port or pin was damaged. Seen this about five times total in life. Mosst of us have tools that will remove the pin but using a vice, even padded better support the inside with short piece of cold roll to keep from risking ending up with an egg shaped barrel extension. Your not going to drive it thru with a punch.

Delete my paragraph on replacing the barrel extension (using a new $10 extension, not replacing pin) as a dozen different scenarios can manifest, of which an improperly headspaced chamber AND misaligned gas port will be likely results. Lack of ability to identify a barrel extension, not know a new one is ten bucks with pin installed, lack of proper tools is a sign. Sometimes giving advice just puts someone deeper in the dirt. Send it to someone who is able to repair and return with headspacing and indexing both in proper specifications.

Get the pin out, it's really this simple, no vice required thus my reluctance to help someone dig a deeper hole.
http://www.practicalmachinist.com/vb/gunsmithing/barrel-extension-204709/

Rather than stock image of extension from Internet, an actual picture of yours might explain to some who's questions are meant to help you what's going on. If going to ask questions beyond standard kitchen table screwing together of in-spec parts pictures, explanation of issue and end goal will only get you better information. If proper questions are asked will be happy to help walk someone through process.