Threads Not Concentric On My 8" AR? - Page 1

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[ARCHIVED THREAD] - Threads Not Concentric On My 8" AR?

Posted: 9/15/2017 8:33:22 PM EDT

Sent my Ballistic Advantage barrel to a gunsmith to check if it was GTG for my Omega 300, and apparently it isn't.

His email: "The threads are off almost .005. I would NOT put a suppressor on that barrel."

He suggested cutting and re-threading, but that would put it under the minimum length that the Omega requires for warranty.

I didn't think this was too common with AR barrels, especially one from a reputable company.

Wouldn't this be considered a defect?

Posted: 9/15/2017 8:36:30 PM EDT

[#1]

Who knows. But I'd post in their industry forum.

If it were me, I'd sell my three BA barrels tomorrow if they didn't at least make an attempt to fix me up

Posted: 9/15/2017 8:36:51 PM EDT

[#2]

What did Ballistic Advantage say?

Posted: 9/15/2017 8:42:25 PM EDT

[#3]

Quote History

Quoted:
What did Ballistic Advantage say?

View Quote

Just got the news today and didn't have time to call them during normal hours.

Not sure if they're open on Saturday, but will give them a call in the am.

Posted: 9/15/2017 8:43:26 PM EDT

[#4]

Contact BA and let them know your gunsmith's findings. ~~I'd expect at least an order of magnitude better on the runout.~~ (n/m - re-read your post - I thought you had said 0.05 runout ... 0.005 should probably be OK)

Stuff happens ... I received a BA .300 BLK barrel that had dinged up threads that probably happened somewhere at the factory (assuming the rubber caps they put on before the barrel left the factory stayed on) and they replaced the barrel without issue.

Posted: 9/15/2017 8:48:53 PM EDT

[#5]

A Post-it note is .004 thick.

A black hair is around .0045-.005

If he measured .005 of run out with an indicator, that is really only .0025 off of center

I would be very surprised to find a production shop making these barrels actually taking the time to dial in the bore, instead of throwing the barrel into a 3-jaw or collet holder

I'm not a gun Smith, just a young machinist, but if someone told me not to use a suppressor because the barrel threads are .0025 off center from the bore, I'd laugh, tell them to have a good day, and then go shooting

Posted: 9/15/2017 8:54:36 PM EDT

[#6]

Quote History

Quoted:
A Post-it note is .004 thick.

A black hair is around .0045-.005

If he measured .005 of run out with an indicator, that is really only .0025 off of center

I would be very surprised to find a production shop making these barrels actually taking the time to dial in the bore, instead of throwing the barrel into a 3-jaw or collet holder

I'm not a gun Smith, just a young machinist, but if someone told me not to use a suppressor because the barrel threads are .0025 off center from the bore, I'd laugh, tell them to have a good day, and then go shooting

View Quote

I haven't a clue about this stuff.

You think it would be fine?

I shot an email over to BA.

Posted: 9/15/2017 9:31:25 PM EDT

[#7]

I asked this question via their website:

Comment: I'm looking at your 11.5 inch, 5.56 barrel and want to know if the threads are concentric to the bore? I want to mount an AAC M42K silencer to it. Thanks.

This was the reply:

You should have no issues mounting a suppressor to any of our barrels. Before the threading operation begins, the bore is verified to be running true for every barrel.

Thanks,

Tony Lenyo
Ballistic Advantage, LLC
2516 JMT Industrial Dr.
Units 106-109
Apopka, FL 32703

That was over a year ago and about 1K rounds through it with my suppressor. No issues at all. I did verify concentricity with a suppressor alignment rod. YMMV. I'd verify your gunsmith findings with BA.

Posted: 9/15/2017 9:49:49 PM EDT

[#8]

I came here to say the same as above, five thousandths is probably not a concern.

What did your gunsmith say is acceptable?

What does BA say is acceptable?

It may be within tolerance. Your gunsmith may want to sell additional services. Or it may not be in tolerance. I'd let BA take care of it if it is out of spec. Keep us updated when you hear back from BA.

Posted: 9/15/2017 9:56:19 PM EDT

[#9]

What did your gunsmith say is acceptable? Haven't spoken directly with Steve (Adco) yet.

What does BA say is acceptable? Just got the email from Adco today, and just sent an email to BA.

It may be within tolerance. Your gunsmith may want to sell additional services. Or it may not be in tolerance. I'd let BA take care of it if it is out of spec. Keep us updated when you hear back from BA. Will do.

Posted: 9/15/2017 10:07:42 PM EDT

[#10]

So ADCO vs BA! Reputable company throw down!

Gets out popcorn.

Posted: 9/15/2017 11:19:49 PM EDT

[#11]

Adco certainly knows their way around a machine shop. Not trying to sound like a jerk here but is there any way they said it is fifty thousandths (.050") out and you typed five thousandths (.005")? Either way I hope for a speedy resolution!

Posted: 9/15/2017 11:22:03 PM EDT

[#12]

"Off by .005" doesn't tell the entire story.

Off, as in: eccentric (parallel axis but offset) to the bore by .005"? That's nothing with a 5.56 and a .30 cal can. Not even a total fail with a .308 on a .30 cal can; unwanted, yes, but usable.

as in: runs out .005" from the bore, measured 6-8" from the muzzle? Also nothing of great concern, unless you're seeking ultimate long range accuracy.

as in: runs out (off the bore axis) .005" over the ~.600" length of the thread? That's quite a bit, and might not pass a range rod test, depending on the length of the suppressor.

A range (alignment) rod would quickly show you if the barrel needs to go back to BA.

Posted: 9/15/2017 11:45:53 PM EDT

[#13]

Quote History

Quoted:
Adco certainly knows their way around a machine shop. Not trying to sound like a jerk here but is there any way they said it is fifty thousandths (.050") out and you typed five thousandths (.005")? Either way I hope for a speedy resolution!

View Quote

Thanks, Rip.

Quoted verbatim:

"The threads are off almost .005. I would NOT put a suppressor on that barrel."

I need to speak to Steve personally, but this seems to be a pretty definitive statement.

I did call Adco earlier, but he wasn't in.
I did speak to another employee who suggested maybe a cut and re-thread, but he wasn't familiar with my exact situation since he wasn't the one who worked on my barrel.

Posted: 9/16/2017 1:38:11 AM EDT

[#14]

I've used ADCO and have BA barrels and have no complaints for either company. That being said, before spending more money having the barrel cut, why not give BA the opportunity to look into your issue? This is from their website:
Warranty

If for any reason you have a warranty issue with one of our AR replacement parts, please contact us at 1-407-347-4584 or go to the Contact Us page and fill out the form. Be as detailed as you can and it is helpful to include images.

Please describe your situation, include your name and order number or transaction id. One of our technical specialists will then review your claim and contact you within 3-5 business days.

If you have images to send, please send them to Contact Us

and include your contact information and, include your phone number

I know you sent them an email, so let us know how they handle it.

Posted: 9/16/2017 2:51:39 AM EDT

[#15]

Quote History

Quoted:

I haven't a clue about this stuff.

You think it would be fine?

I shot an email over to BA.

View Quote

Get an alignment rod, it will be far more accurate than any internet guess

Posted: 9/16/2017 6:32:01 AM EDT

[#16]

As others have stated, this is best handled by BA. They're a great company and I'm sure they'll explain to you their tolerances and their recommendation of max runout for mounting a suppressor.

ADCO is very highly regarded around here, has been for over a decade, so I would trust what they say vs anyone else on here.

I would hope that BA tells you to send the barrel back to them for confirmation of concentricity and that they'll swap it out if it's unsafe or questionable.

I just bought an 8" BA 300BLK barrel so curious how this goes.

Posted: 9/16/2017 7:04:40 AM EDT

[#17]

Forgive me if this is dumb, but I want to learn. Why bother having the threads checkedat all? What I f the threads are good, but the shoulder isn't perpendicular? What if both are good, but the suppressor adapter is bad? What if the muzzle is good, the adapter is good, but there's a suppressor issue?

Wouldn't a better, all encompassing check be an alignment rod or looking down the bore with the actual intended barrel, mount, and suppressor?

Posted: 9/18/2017 10:35:51 PM EDT

[#18]

Ballistic Advantage contacted me today and basically said that it was strange, and asked how Adco measured the threads--or if they documented it.

I forward that to Adco, and I think the guy got a little insulted.

"You need to ask to talk to someone who knows that they are talking about. There is only 1 proper way to check a barrel to see if the threads are concentric to the bore. The OD of the threads is more than .004 off center of the bore."

IDK.
I'm not choosing sides or wanting to get in the middle, I just want to know if there's a significant risk of a baffle strike using this barrel. If so, then I think BA should address it.

Posted: 9/19/2017 12:00:11 AM EDT

[#19]

Quote History

Quoted:
Ballistic Advantage contacted me today and basically said that it was strange, and asked how Adco measured the threads--or if they documented it.

I forward that to Adco, and I think the guy got a little insulted.

"You need to ask to talk to someone who knows that they are talking about. There is only 1 proper way to check a barrel to see if the threads are concentric to the bore. The OD of the threads is more than .004 off center of the bore."

IDK.
I'm not choosing sides or wanting to get in the middle, I just want to know if there's a significant risk of a baffle strike using this barrel. If so, then I think BA should address it.

View Quote

The thing about ADCO and it sets some people off is that they "know what they are doing" and sometimes it can be hard for them to accept that something was done wrong by accident. But they do get a lot of nonsense through emails every day....so I can understand their point of view. You more than likely are talking to a customer service rep and not a machinist through BA.

Hard for me to believe BA wouldn't take care of this properly though considering they are a barrel manufacturer

Not blaming fault or anything on ADCO....just weird that its a back and forth game.

Posted: 9/19/2017 3:33:22 AM EDT

[#20]

Quote History

Quoted:
Get an alignment rod, it will be far more accurate than any internet guess

View Quote

This. I don't have a clue who's right or wrong in your case but if you're willing to mail off barrels to have them checked getting an alignment rod seems like a small investment.

The whole thing kind of reminds me of an issue I had recently. I sold a new Colt 6920 upper (minus BCG) to a guy and later he tells me he had a gunsmith check the headspacing (

) and it failed. After a LOT of back and forth we figured out the gunsmith didn't know what he was talking about (shocking) and the upper was just fine. Huge headache over nothing.

BA's response seemed kind of wishy washy. I figured they would have said, "Yep, if that's accurate it's out of spec, let us check it out" or "No, that's within acceptable limits, ADCO is full of it."

Posted: 9/19/2017 3:38:12 AM EDT

[#21]

ADCO has a very good reputation, but if they are getting pissy about being asked how they took their measurements, they need to calm down.

Fact is that asking how they took their measurements and what gauging they used is a valid question that anyone who does machine work should be prepared to answer.

Can you ask them what tolerances they call acceptable on the concentricity for the muzzle threads?

Posted: 9/19/2017 4:21:56 AM EDT

[#22]

Quote History

Quoted:

I forward that to Adco, and I think the guy got a little insulted.

"You need to ask to talk to someone who knows that they are talking about. There is only 1 proper way to check a barrel to see if the threads are concentric to the bore. The OD of the threads is more than .004 off center of the bore."

View Quote

The OD of the thread doesn't matter so much as you typically don't have over 80% thread engagement. The concentricity and parallelism of the pitch diameter is what should matter . . . and that is not easy to check. I would think the best way would be to install a calibrated gauge (female threads and ground OD) on the barrel and then indicate that.

Posted: 9/19/2017 7:30:46 AM EDT

[#23]

I'm curious how they checked it. "Only one right way" Put it on the CMM and take a gazillion points?

Posted: 9/19/2017 9:44:13 AM EDT

[#24]

Quote History

Quoted:
I'm curious how they checked it. "Only one right way" Put it on the CMM and take a gazillion points?

View Quote

This made me laugh. I think this conversation happens everyday between machinists/QC in the machine shop at my employer. The machinists are typically either extremely right, or they scrapped a part. Not much in between when it elevates to this level of discussion.

Posted: 9/20/2017 10:06:19 PM EDT

[#25]

Will 5 thousandths of run out even matter?

That's a really small amount and cans usually have quite a bit of clearance when compared to 5 thousandths

Posted: 9/20/2017 11:27:34 PM EDT

[#26]

Quote History

Quoted:
Will 5 thousandths of run out even matter?

That's a really small amount and cans usually have quite a bit of clearance when compared to 5 thousandths

View Quote

That's all I'm trying to find out.

Still waiting to hear back from BA. In the meantime, I duped this in their forum.

Posted: 11/14/2017 9:31:48 AM EDT

[#27]

Update:

BA replaced my barrel with absolutely no hassle.
Thank you Kyle!

Posted: 11/14/2017 11:40:58 PM EDT

[#28]

Glad they took care of you.

Posted: 11/15/2017 9:49:50 AM EDT

[#29]

Warranties or specifications aside, I personally would not mount any suppressor on an 8" 5.56x45 barrel for two reasons.

First is the minor one of the pressure in the entrance chamber of the suppressor will be twice what it would be with a 14.5" barrel. This, of course, can be compensated for with increased material strength in manufacture. Flame temperature is higher, powder particles continue to burn in the entrance chamber, and baffle erosion is accelerated (even with inconel)

Second is an issue of bullet stability. Tribal knowledge says that one needs at least one complete revolution of the bullet in the rifling for stability, and you just don't have that in an 8" barrel since the chamber and throat take up 2", and I doubt that any of these barrels have a twist tighter than 1:7. In addition, you need a certain rotational velocity to stabilize, and the muzzle velocity in an 8" barrel is considerably less than in a longer barrel. Further, the M855 (green tip) ammo uses an intentional marginally stable bullet design.

Chances of an endcap or baffle strike go up significantly as the barrel shortens, and even more so with full auto fire.