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Posted: 10/26/2004 10:34:35 AM EDT
Hi, I'm new here. I have a few questions about the AR-15 barrels that I can't seem to find via the search function, and I don't really want to pull my barrel to find out.

I'm looking for info on the thread diameter and pitch used on the chamber end of the barrel to attach the barrel extension (with the locking lugs)

Also I'm looking to find out the diameter of the barrel extension where it slides into the upper receiver. maybe one of you guys has an extra barrel or upper laying around you could measure with a caliper.
Link Posted: 10/26/2004 10:52:45 PM EDT
Link Posted: 10/27/2004 2:47:20 PM EDT
.810x16 threads on a .620 shank. Extension diameter: Colt 1.000, DPMS .999.

Link Posted: 10/27/2004 2:49:05 PM EDT

Originally Posted By cwtoyota:
Maybe one of you guys has an extra barrel or upper laying around you could measure with a caliper.

Nobody here has extra barrels hanging around. What do you think this is..................... I haven't measured one lately but the above numbers look close. Maybe I'll go check..................
Link Posted: 10/27/2004 4:33:20 PM EDT
I have a couple of barrels the barrel extensions are removed they are used military ones intersted ?
$25.00 shipped to you , now befor you get all hyped up these barrels NEED WORK ! if you want to use them you will have to have a lathe and a lot of time it is a real pain in the A _ _ to index the barrel extensions to the gas port and get it right if you can not do this your just throwing you $$ away
Link Posted: 10/28/2004 10:08:24 AM EDT
Thanks for the help guys!

I'm actually looking for a barrel extension or two and the barrel nuts to go with them. I have a barrel that I want to use on an AR-15 caliber conversion upper.

Link Posted: 10/28/2004 2:13:01 PM EDT
Ah, a do it yourselfer. Welcome. Here's a little more info that applies to the .556 chamber. The bevel leading into the chamber is 29-30 degrees and has an outer diameter of .570-.650. You need .1 thread relief at the barrel shoulder.

Finish chamber depth can be measured by putting the gauge in the chamber and screwing the extension on with the stripped bolt in place. The gap between the barrel shoulder and the extension is measured with feeler gauges and that's how much farther the chamber has to be cut - add a little for crush.

Link Posted: 10/28/2004 3:28:24 PM EDT
have all parts in stock give me an email ddonley@erols.com
Link Posted: 10/28/2004 5:46:10 PM EDT
[Last Edit: 10/28/2004 5:46:51 PM EDT by cwtoyota]
Thanks for the extra info olephart. I want to do a few upper conversions, and it seems that the best way is to just get the parts and try it.

Gunrunner1000, I sent you an E-mail.
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