Barrel Extension Source

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11 years 5 months ago #25552 by 13fcolt
Replied by 13fcolt on topic Barrel Extension Source
What everyone else said.
Installing a barrel extension requires timing the threads and finish reaming the chamber so that head-space, index pin,and gas-port all line up as they should.

A mass production barrel gets it's gas port last, drilled in line wherever the index pin happens to be. A new barrel extension could fit, but the pin may not end where you need it. So it's not something that can just be switched out.
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11 years 5 months ago #25557 by faawrenchbndr
Replied by faawrenchbndr on topic Barrel Extension Source
Thanks for the insight 'Colt

Did not know about the gas port being machined last, learn something new everyday!

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11 years 5 months ago #25578 by pookybear308
Replied by pookybear308 on topic Barrel Extension Source
13fcolt, I thank you as well...those are the details that have done the trick. I will start looking for something more complete.

That said, would it have helped at all if the seller of the barrel still had the original barrel extension? Just wondering for more complete future reference.

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11 years 5 months ago #25581 by faawrenchbndr
Replied by faawrenchbndr on topic Barrel Extension Source
Not to sound rude but I can not believe he sold you a barrel without an extension. I have never seen one 1st hand without an extension. I would suspect, shy of sending it to a shop like ADCO I'd say you are screwed on that barrel.

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11 years 5 months ago #25586 by Lizardette
Replied by Lizardette on topic Barrel Extension Source
No one has said anything that's wrong. Not at all.

Still, I'm a devil's advocate by nature, so here goes:

Checking headspace and if necessary finish chambering a .308 Win/7.62x51 barrel (or any other for that matter) is not that difficult if you have the right tools.

In fact, headspace gauges and finish reamers can be rented online with a minimum of hassle. I've used both 4-dproducts.com/ and www.reamerrentals.com/default.asp successfully.

Timing a barrel that doesn't line up right on its own can be more problematic, but isn't outside the realm of possibility if you have access to a lathe.

----

Should I continue with an explanation of what's involved?
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11 years 5 months ago #25590 by SOC
Replied by SOC on topic Barrel Extension Source
You can time an extension to a old barrel by taking a sanding disk and opening up the hole so the threaded portion of the barrel just fits through.

Thread on the extension tell you come against the disk then start turning the disk to remove material from the extension.

A washer between the disk and barrel will prevent you from sanding the barrel.

It can be very time consuming if the extension is not a close fit, but can be done.

I timed a FAL barrel to a new receiver this way but they were already a very close fit.

Go slow and don't overdo it.
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11 years 5 months ago #25607 by pookybear308
Replied by pookybear308 on topic Barrel Extension Source
OK folks...you win.
I will assume that I got hosed on this "bargain" barrel and move on to something more complete. The time, effort, and parts required to do this barrel right are beyond it's worth, I'm thinking. :(

In the meantime, however, I will ask the seller if he still has the original extension. By now it can do no harm and might be enlightening.

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11 years 5 months ago #25608 by Lizardette
Replied by Lizardette on topic Barrel Extension Source
Pooky: incoming PM.

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11 years 5 months ago - 11 years 5 months ago #25609 by Lizardette
Replied by Lizardette on topic Barrel Extension Source
Talking with a friend who's much more an expert in the technical matters than I am:

It seems that the threads are different between the Armalite and DPMS extensions. The outside dimensions are apparently the same though. [strike]Word is that the bolts interchange as well.[/strike] The carriers may have issues though, regarding the forward assist cuts.

Edit: Found conflicting information. Will update when I know more.
Last edit: 11 years 5 months ago by Lizardette.
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11 years 5 months ago #25618 by faawrenchbndr
Replied by faawrenchbndr on topic Barrel Extension Source
I have heard the bolt carrier groups, AR10 vs 308 are interchangeable, but not recommended.
Have never seen a solid answer,......please post what you find.

Just for the record,....I can not/will not recommend anything DPMS!

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