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Posted: 8/13/2010 6:52:38 PM EDT
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A number of years ago, I had a 1/12 twist barrel on my "spacegun" replaced with a 1/8 twist.
I received the old barrel back but without the barrel extension. I have a new barrel extension that I'd like to use on this barrel however when screwed on, the registration is off by 3/4 of a turn. Should the shoulder be turned so that barrel lock-up registers at 12 o'clock for both barrel extension pin and the gas port? I called ADCO to see if they'd install and they declined. I'd like to use the barrel on a new upper for varmint. Thanks, Dennis |
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Once a barrel extension is removed from an AR barrel you effectively have a paperweight.
Unless you can do the barrelsmithing yourself to fit the barrel extension, retime, rechamber, etc, it will cost more in labor to have it done than the cost of a new barrel. That's probably why ADCO refused the job as will most other shops. If you wanted to preserve the old barrel you should never have had the extension removed. Every month when this subject comes up, I renew my suggestion that manufacturers spot weld the extensions onto the barrels during manufacture. |
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The barrel extension will dictate not only the head space, but the bolt lug void area as well.
So lets say that the extension indexes short or long of the needed index mark (barrel gas port), if you are going to set back the barrel thread shoulder, then you may need to set back the barrel breach face as well. Now once you have the extension pin indexing with the barrel gas port with the extension torqued to Plus175 ft lbs, and the inside of extension lugs to breach face correct as well, you will need rechamber the barrel to get the head space correct as well. Not saying that it can not be done since I have done it myself (have my own shop), but from a cost effectiveness with someone else doing the work for you and charging for such, it will be cheaper to just buy a new barrel instead, |
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