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Posted: 1/4/2003 4:53:27 PM EDT

almost finished with my first ar.   might be a dumb question but, when i thread my barrel extention onto my barrel the barrel index hole dosn't match up w/ the top of the barrel.  am i doing something wrong when i thread it on?


Link Posted: 1/4/2003 5:52:38 PM EDT
Exactly what do you mean when you say, "when i thread my barrel extention onto my barrel the barrel index hole dosn't match up w/ the top of the barrel" ?

Not sure why you purchased the barrel and extension separately.  Normally during production / assembly the barrel extension is torqued onto the barrel blank, the gas port hole in the barrel (under the front sight base)is located and indexed off of the barrel extension pin and drilled through to the bore, the front sight post is also indexed off the barrel extension pin and the two taper pin holes are drilled.  Lastly the headspace is checked and the final chamber finish reamer is used to obtain the correct headspace.

It sort of sounds like you bought the barrel extension and barrel separately and unfortunately the barrel might have already had the gas port drilled and front sight post installed.  Is this your situation?

Unless you REALLY understand the working relationship of the parts I have mentioned and own a very good lathe and chamber reamer, then I would suggest you go buy a COMPLETE barrel assembly from a reputable dealer / parts vendor that is ready to install on your upper receiver without further work required.
Link Posted: 1/4/2003 8:58:40 PM EDT
i bought the barrel off of my buddie and the extention was already on the barrel.  i didn't even take notice whether or not the pin hole was aligned at the top or not when it was on.  i removed it and put it back on.  i'm thinking that i could buy a new extension and see if it fits up.  if not, i'm guessing that i could grind an index pin down into the hole that is there, then either bore an new hole into the the index hole and drill a new one, filing down the inside of the extention also in the new area.  sound about right?


Link Posted: 1/4/2003 10:15:20 PM EDT
The barrel extension pin is drilled top center of the feed ramps.  If you relocate the pin, then the feed ramps and lugs will not be indexed with the upper/bolt.

Your best bet is to send the barrel off and have a smith re-install the barrel extension to 175 lbs of torque, then weld the gas hole closed, and re-drill the gas hole and re-mill the front sight slots per new index.  
Also, since the barrel extension dictates the barrel headspace, this too, will need to be checked, and corrected if needed.

Link Posted: 1/4/2003 11:55:40 PM EDT
dude it'll be alot cheeper to buy a new barrel!
Link Posted: 1/5/2003 4:03:44 AM EDT
Originally Posted By Dano523:
...re-install the barrel extension to 175 lbs of torque...
View Quote

That's an awful lot of torque...I'm fairly certain any piece of round stock held in my vise or even in my lathe chuck will slip before reaching that figure...
Link Posted: 1/5/2003 4:55:37 AM EDT
Originally Posted By stingerjg:
dude it'll be alot cheeper to buy a new barrel!
View Quote

I think I would have to agree with stingerjg.  You will be better off forgeting about that barrel and get a new one.  Then you know it will be right.  Hope you didn't pay a lot for that barrel!!
Link Posted: 1/5/2003 5:00:40 AM EDT

Suggest you just buy a new barrel, with the extension already on it and properly headspaced. I don't understand how you ever removed the extension from the barrel--that takes major force.

Link Posted: 1/5/2003 10:51:51 AM EDT
sounds good,

looks like i'm getting a new barrel.

thanks alot for the help,

Link Posted: 1/5/2003 3:55:10 PM EDT
You might be able to still use it for a 22LR conversion using the Ceiner kit, but it would only be good for a "blaster" barrel as it is just bit big in dia for the 22. It still should work though.
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