Cross-threaded barrel at muzzle

[Halimar]

I bought a new LaRue AR-15 a few years ago and took it into a local Atlanta gunshop for replacement of the flash suppressor. I recently decided to upgrade to a new CrossFire suppressor. I looked at the CrossFire instructional video on how to replace one, watched a few other YouTube videos, and talked to someone I know who had recently replaced the suppressor on their AR. It all looked and sounded straightforward to me, so I decided to do it myself.

I bought a receiver block to properly hold the barrel without damaging the reciever, bought a multipurpose AR-15 wrench, got the appropriate solvents and thread lock, and checked myself in to my dad's (God rest his soul) workshop to get started. I set up my laptop on the bench and watched the SureFire video twice more before even starting. Almost immediately after applying wrench to suppressor, the problems began.

I had to put almost all my muscle into getting the suppressor to break free. It finally did with a loud "POP". I took the barrel out of the assembly to inspect the receiver, thinking I'd cracked it. I didn't see any damage, so I chalked it up to old thread lock and began again. To my and the barrel's dismay (the metal was "groaning" pathetically), I was wishing Hoss Cartwright was there to wrench it off for me. It was a real struggle, and continued to require that I give it everything I had - and to my dismay the metal continued to groan all the way out to the end.

When I got the thing off I immediately saw the problem. It had been cross-threaded! I then knew why the instructor in the CrossFire video had said two or three times to take the barrel out of the vice and hold it so the muzzle is pointing straight up before screwing the new muzzle brake on...so you don't cross thread it. I saw that, but a gunsmith didn't know it??

Questions:

1) Can a good gunsmith fix crossthreads in that location? Only about a 1/3 of an inch of the threads appear to be damaged.
2) Can a good gunsmith tell if I damaged the barrel taking the old flash suppressor off? I tried my best to turn force on the center of the bore so as not to apply lateral pressure on the barrel, but I was afraid I was going to twist the thing like a swizzle stick.
3) Can anyone recommend a good AR-15 gunsmith (ideally in Atlanta)? Or does anyone know where I can find a listing of the best gunsmiths?

This only happened this evening, so I haven't decided what to do about the gunshop and their loser gunsmith. Based on a transaction that took place shortly after they installed the flash suppressor, I resolved myself never to set foot in that shop again - and I haven't. However, before that I had unfortunately bought several firearms from them. But I do want to forewarn others lest they spend their hard-earned money there, and run the risk of having their valuable firearms damaged. Ultimately it's my fault for trusting a gunsmith I hadn't vetted.

 

[Bobby Bailey]

If the threads are damaged , it is best to remove that section and re-thread. Any good gunsmith can handle that. Checking to see if you bent the barrel (most likely you did not ) is as easy as shooting it. The action/barrel junction can be checked for damage or looseness. I can't help with the location. We're not that far from Atlanta, Tx. but we're a ways from Atlanta, Ga. ;D
Bobby

 

[hmcsr]

Might want to talk with Frank or Theresa White of Compass Lake. They are located in Alford, Fl on the panhandle. http://www.compasslake.com/

 

[jscandale]

Halimar,

Got a question...how does the threaded socket look in the suppressor itself? Are the threads in the socket also mangled? Rethreading a barrel isn't hard at all if the barrel is properly chucked up in a lathe and the centerline of the bore is indicated and the threaded tenon is cut properly. The one major issue that I can see is if the old mangled tenon is cut off and a new tenon is recut, will it make the barrel shorter than the legal minimum of 16"?
In any regard, that is something that Frank White or myself or an decent gunsmith could do in their sleep. Frank is closer to you though and he is a great guy and a good friend.

JS

 

[Halimar]

JS,

First I want to say that upon re-reading my post I see that spell-check changed "SureFire" to "CrossFire" - along with some other random word replacements that leave me scratching my head. However, you obviously understand the potential consequences and cures - far better than do I. So enough said about that.

As to your question, I couldn't tell what the threads looked like on the device itself. For the sake of brevity I called it a "suppressor" in my posting, but since you asked that specific question, it's actually a SureFire Muzzle Brake / Suppressor Adapter (MB556AR). The sleeve that fits back over the throat of the barrel on that particular model adapter - designed to shorten the overall length of the rifle with suppressor mounted - is far too long for me to be able to fully examine the extent of damage to the threads, which are deep within the adapter. However, by shining a flashlight down inside, I can see that they are discolored. But by the awful metal-on-metal noise made when removing it, I assume the worst.

I have sent an e-mail to www.accurateordnance.com describing the problem and asking them for their thoughts. I found them on a thread at www.ar-15.com, and they are located here in Atlanta...I don't know anything about them other than what is on their website.

Depending on how much the repairs will cost and if the barrel itself is damaged, I may need a new barrel. I hope not but if that becomes necessary, and depending on the wait, I'm thinking either a Satern or a Noveske. I'm assuming LaRue doesn't use a propriety barrel and both of those will retrofit. If it comes to that, I guess I'd need to contact LaRue and ask them what I should do. Perhaps I should see if they will replace it, though I don't see barrels on their website.

Hal

 

[Rustystud]

There could be several issues and not have been cross threaded, some are as follows:

The threads could have been gaulded due to no grease or anti seize.

One side may have been 24, 28, 32, 36, or metric tpi and the other a different thread.

And yes you can bend a barrel it is not that hard to do.
Nat Lambeth

 

[Halimar]

Nat,

I think you are right, and the damage to the threads is due to galling versus cross threading. The (sub)definitions for galling found at www.dictionary.com:

"Machinery . (of either of two engaging metal parts) to lose metal to the other because of heat or molecular attraction resulting from friction." A second definition refers to

"Metallurgy . (of a die or compact in powder metallurgy) to lose surface material through adhesion to the die."

It looks like the appropriate description of the source of the problem would be found in the definition specific to machinery. (The other looks to apply to resizing dies reacting to brass cases.)

Upon going back and looking at the SureFire installation instructional video yet one more time I see that the muzzle is positioned vertically to allow the washer and shim to align horizontally flush against the barrel, and not to reduce the risk of cross-threading as I thought I remembered when writing my original posting (rant). Continuing with a review of the instructions, there is no mention of lubricating the threads. However, use of Rocksett on the threads - both on the barrel and on the device - is specified. The included tube of Rocksett is simply labelled "SureFire", but based on information found at http://justshootmeproducts.blogspot.com/2008/06/using-correct-adhesivethread-locker-can.html, I assume it is Flexbar Rocksett Ceramic Adhesive which that site states will withstanding very high heat and thus is suitable for use on firearms.

I re-inspected the affected threads on the barrel and did see some occlusions, but that does not necessarily mean that it was crossthreaded.

Thanks for the insight.

Hal

 

[Greatwhitenorth]

Could be some original threads were turned to be a tight fit and some galling occured in the connection. A slight clearance is required on the male female pitch diameters along with min/max diameters of the peices. It is also possible there is a slight difference in the TPI that would allow several turns until it binds. This would be evidenced by some thread stretch on the softer of the two materials. See if an appropriate tap and die can clean them both up. If there is a TPI difference clean up the barrel to its proper pitch. Re-thread the suppressor to match. You will lose some threads in the process but as long as most of them grab, you should still be alright.

 

[jscandale]

Hal,

Have you called LaRue about the problem?

JS

 

[Halimar]

After speaking with a local gunsmith earlier this afternoon I got a bit discouraged from what I thought sounded like half measures, so I did call LaRue. I explained what happened and what I'd learned here. I also told them I really did not think it was a warranty issue -- that I was confident the damage was due to carelessness on the part of the gunsmith who installed the MB556AR. (I mean, we're talking about LaRue and SureFire here, so I'm going to give them the benefit of the doubt.)

The guy I spoke with asked me the name of the gunshop where the work was done, and then put me on hold. He came back a few minutes later and asked me to send him a closeup photo of the threads and a written explanation of what transpired start to finish, which I just did. He said that once they received that information and had a chance to look at it, they'd get back to me with a solution. He said they needed to receive the requested information first, but if everything was like I described to him over the phone they'd likely want me to send them the upper (LaRue Tactical 5.56 Stealth Sniper System LT011) so they could "swap out the barrel." I'm thinking that whatever they recommend is the best way to go, and that if I'm going to buy a new barrel I'd rather keep the upper 100% LaRue.

I guess I could've called them from the start, but it's taken me awhile to get to this level of understanding of the situation. And I have no idea where I'd be in the process were it not for the excellent advice I received here in this forum.

Hal

 

[Halimar]

As I stated in my previous post, I called LaRue on Monday. By then I had resolved myself to replace the barrel. I hoped that because of the extenuating circumstances they would sell me one at a reasonable price, but I was a concerned because they do not advertise barrels for sale on their website. How much does a LaRue barrel cost? I didn't know, but I would've been willing to double up on a bet that they weren't cheap. Well, LaRue called me back this morning and I found out.

They said they'd looked at the photos, read my description of how I had to struggle to remove the muzzle brake, talked about it amongst themselves, and decided it would be best to just go ahead and replace the barrel. In a sense I was relieved since this, as mentioned above, confirmed my own opinion - actually arrived at after a conversation with a local gunsmith and precision barrel maker who said that since it's a semiautomatic, go shoot it and see if it is reasonably accurate. If it is, bring it in and we'll re-thread it. If not, then get a new barrel, but don't spend too much on it since it is, after all, a semiautomatic.

I am probably wrong on this next suggestion, just as I was wrong thinking the threads on my barrel were cross-threaded. (Thanks for correcting my mistake Nat and Greatwhitenorth!) But I really can't believe he thought so little of semiautomatics. Instead, I think he had me pegged as a plinker. And you know what? He was right. But despite my lack of shooting prowess, I wish he'd considered that I thought enough about quality firearms to plunk down the cash needed to buy all the components and accessories for an AR-15 from LaRue...except for the NighForce optics because LaRue didn't sell them. I mean, just because I'm not a bone-in-the-teeth shooter doesn't mean I don't want to maintain the integrity of a fine firearm. But wrong about his perspective or not, I was pretty discouraged. I thought to myself, I bought this awesome LaRue weapon system - worthy of an active duty soldier in combat (except, regrettably, no happy mode), and I'm not going to compromise it.

Anyway, LaRue called me this morning and said that I should send them the upper because they decided it would be best to replace the barrel. I took a deep breath and asked how much. I was thinking at least $600, but maybe as much as $900. He said, I don't know. That really depends on the size of the box and how you send it. But do be sure and wrap it securely and put a lot of insurance on it because if it's lost in shipment we can't be help you. I said, No. How much to replace the barrel? He said, Oh, there's no charge for replacing the barrel. And, oh yeah, send that SureFire flash suppressor you want to install along with it. We don't know who you're using for a gunsmith or if you're planning to do it yourself, but we all agreed that we want to put it on ourselves (followed by a hearty laugh). But be sure to separately wrap it - preferably with bubble wrap - so it's doesn't come into contact with the upper during shipment.

I guess they, like the previous gunsmith, had me pegged as a plinker. But this time I laughed, too.

Thank you LaRue. And thanks for everyone's input here.

Hal