AR Gurus: Bad barrel extension, barrel crooked

[miket]

I was sighting in a used 6.8 upper that I bought and to make a long story short the POI was way left. I started checking things out and it appeared as if the barrel and handguard was bent. I pulled the handguard and put a scale along side the rail and the barrel was obviously cocked. I pulled the barrel and checked everything out and when I set the barrel on the upper it didnt sit square. I put the upper on my granite inspection table and ran an indicator down and around ( too hard to explain ) and the upper surfaces are square and flat. Then I put the barrel on v blocks and put the indicator on it and the barrel extension was out of parallel .004 Then I checked the thickness of the rim of the barrel extension and it varied about the same amount.

So now what? I am thinking I could pull the pin and turn or mill the rim of the barrel extension ( the part that sits against the upper ) and square it up. I am a machinist so doing it isnt a problem. BUT will that hurt anything? I honestly cant see a problem with it but Im not real familiar with ARs.

What do you think?

[miket]

[ATTACH]757365[/ATTACH]

[ATTACH]757366[/ATTACH]

[JustinJ]

I would have taken it to a gunsmith long ago. Or sent the barrel back to the manufacturer

[miket]

I would have taken it to a gunsmith long ago. Or sent the barrel back to the manufacturer

I could be wrong but I figure sending it back to Bison is out since I bought it used.

[JustinJ]

I could be wrong but I figure sending it back to Bison is out since I bought it used.

I would assume with a company like Bison they would help you out. Maybe some of the lower tier manufacturers wouldn't do anything about it but I'd bet bison will.

[hellbndr23]

Be careful with changes to the pin side of the rim. Someone correct me if I'm wrong, but I believe changing that dimension will affect head spacing.

[miket]

Finally found a drawing for the barrel extension. Except for the .990" dim to the left side of the ring or lip ( or whatever its called ) all the dims come from the right side so if drawn right ( which Im sure it is since it is such a well known, high qty part ) then changing the width from the left side wont affect anything else. I cant see the default tolerance so I dont know if its +/- .005 or what.

[Lungbustr]

I would have them exchange it.

[catslayer]

Worth a call to see if they will help out

Not all gunsmiths are really good machinist....

in fact a lot of machinist are better working the metal than gunsmith, just less specific knowledge of firearms

best gunsmith in the world would be a a 20 year machinist of very fine parts and detail oriented who then decides they want to build guns lol

[miket]

I thought we had more AR gurus here.
I just emailed Bison just to see what they think. It is not their responsibility IMO since I bought it used. If they dont want to deal with it I will do it myself. Should be easy.

[rosco11]

You can always replace it. . Daniel Defense high end barrel or CMMG is my fav that's more affordable. However, I get the sense that u want to fix it and if u have those skills, I'm very envious!

[Tommyh]

I thought we had more AR gurus here.
I just emailed Bison just to see what they think. It is not their responsibility IMO since I bought it used. If they dont want to deal with it I will do it myself. Should be easy.

bison's barrels are only $200 for a 16" SS 6.8 and one of two that i would use. if they wont replace it, buy a new one and move forward.

[miket]

Just a little follow up. I emailed Bison and after verifying that it was one of their barrels they offered to replace it for $100. Not wanting to put more money into it I declined and asked their gunsmith if it was OK to just square it up and that it should clean up with only taking .005" or so and he said that would be fine. I chucked it up in my mill, lined it up and milled it to .125" thick ( to clean up 100% ). I reassembled it and everything is now square and straight. I shot it today and its all good now, love it.

[Colton]

Heck ya! Glad to hear that it worked out for you!

[DaveC]

Good deal, glad you got it figured out.