Barrel Extension Separation!

[Hansel&Grendel]

I've installed A LOT of muzzle brakes/comps for my own rifles and for many others whom I've built rifles for from ground zero. I purchased an 11" 6.5 Grendel Criterion barrel (NFA) from a well known vendor that bores their own barrels but apparently outsources the nitride finish. I clocked a Precision Armaments EFAB brake as usual at 10:30 or 11:00 using peel washers, and then gave a final wrenching all while using a Geissele Reaction Rod.

I recently noticed that the gas block was canted when looking down the muzzle. Very peculiar indeed. I then attempted to remove the EFAB and found that the barrel was rotating away from the barrel extension while using the Geissele Reaction Rod! A first ever for me. I undid the entire upper including removing the barrel nut (ALG Defense in this case). I was literally able to unscrew by hand the barrel extension from the barrel. I carefully clamped the barrel in a vise to eventually remove the EFAB.

I contacted the well-known vendor that sold the Criterion barrel. I was told that without doubt I over-torqued the EFAB and that it's a mistake to use a Geissele Reaction Rod. The vendor machines their own upper vise block by the way. I maintain that there's no way that I over-torqued the EFAB during install to the extent that it caused said separation. I didn't argue and sent the barrel back for barrel extension re-installation along with matching a properly head-spaced proprietary 6.5 Grendel bolt.

I just can't imagine that I applied so much torque value for the brake installation with a Geissele Reaction Rod that caused said separation! What say you as to the likely true cause of the separation?

Thanks, Hans.

[Kswhitetails]

First thought is that if you had applied too much torque to the muzzle device, that you would have tightened the extension, not loosened it. Hard to understand this one. Extensions being loose seems to be a trend around here. Fishy.

[Hansel&Grendel]

Exactly! I ran it by a local Yoda armorer who said the same as you - that I would have instead tightened the extension. The local armorer also said that the nitriding process can somehow manage to loosen a barrel extension.

[FLshooter]

I mostly use a modular vise block w/pins to install muzzle devices.But,I have used a Geiselle reaction rod before I ever got my Magpul bev.I don’t see how you could loosen a barrel extension unless you apply monster torque.
I use my old craftsman half-inch drive beam torque wrench w/custom made adjustable wrench that fits on a half-inch drive. I tighten AR15 barrel nuts at 40 pounds. And although I do not always use a torque wrench to tighten a muzzle devices I would say they are between 30 to 40 pounds max.
From what you posted it sounds like you take great care and installing barrel nuts and muzzle devices like I do .I think that when you got the barrel there was already a problem. They’re just trying to pawn the blame off on you.

[Lemonaid]

If I understand things correctly the alignment pin goes through the barrel extension into the barrel threads, thus pinning it from movement.
So either the pin was sheared or it came loose? (backed out of the divot in the threads)

[Hansel&Grendel]

In this case, the barrel index pin was neither sheared nor came loose. It remained intact on the barrel extension throughout. Separation occurred regardless of the barrel index pin. I do recall that the vendor lost their chief machinist at about the time of my purchase and that those left behind had to quickly learn to the machines to keep up with demand. I also thought to re-visit a bookmark on my computer from a Shooting Illustrated article (12/2017) about nitride barrel finishes; excerpt:
"... the nitriding process tends to loosen up barrel extensions. So, existing AR-type barrels that are treated must have their extensions properly timed and torqued afterward."

https://www.shootingillustrated.com/articles/2017/12/30/the-pros-and-cons-of-nitride-barrel-finishes/

[A5BLASTER]

Dude just spit it out. Who made the barrel?

What's with the secrecy? If a shop has had a issue we want to know who it is so we can track how it's handled.

[mdram]

I've installed I purchased an 11" 6.5 Grendel Criterion barrel (NFA) from a well known vendor that bores their own barrels but apparently outsources the nitride finish.

this part confuses me
if the barrel was bored by the vendor, then its not a criterion
now if the vendor bought the blank, profiled, installed the extension and chambered, that is different.
boring is creating the bore and rifling.

and please do name the vendor

[grayfox]

In this case, the barrel index pin was neither sheared nor came loose. It remained intact on the barrel extension throughout. Separation occurred regardless of the barrel index pin. I do recall that the vendor lost their chief machinist at about the time of my purchase and that those left behind had to quickly learn to the machines to keep up with demand. I also thought to re-visit a bookmark on my computer from a Shooting Illustrated article (12/2017) about nitride barrel finishes; excerpt:
"... the nitriding process tends to loosen up barrel extensions. So, existing AR-type barrels that are treated must have their extensions properly timed and torqued afterward."
https://www.shootingillustrated.com/...rrel-finishes/

The real point being made here is that the proper technique is to nitride the barrel first, then install, torque and time the extension/alignment pin, afterwards. Since the barrel and the extension are usually 2 separate alloys, their heating/cooling coefficients will differ and the nitriding process will cause them to loosen at times. So this guru-shop must not be as guru-good as supposed. I would strongly consider shopping elsewhere.

[Lemonaid]

If who ever did the barrel drilled through the extension and into the barrel and the index pin goes through the extension and into the barrel there is no way the extension can either tighten or loosen unless the pin has sheared or the pin has came out of that drilled hole in the barrel.
In your case either the hole was never drilled into the barrel or not deep enough or the pin popped out of that hole.
They are assembled that way with a tight fitting pin to make it near impossible to take the extension off without drilling out the index pin.
This link may be of interest: https://rifleshooter.com/2014/05/bui...-from-a-blank/

[Hansel&Grendel]

The barrel was indeed bored by Criterion with the barrel blank work performed by PF in Martinsburg WVA. Yes, I'm a bit disappointed that I was told that I over-torqued the EFAB and that it was a mistake to use a Geissele Reaction Rod. I've lost count of how many brake/comp installations and builds from ground-zero that I've performed. I don't over-torque brakes/comps or barrels. As said, I clock brakes/comps at 10:30 - 11:00 for a final wrenching. PF is taking care of it, and I've had great success with them in the past, but in all honesty I don't understand how I could have over-torqued without a running start and why it's such a bad thing to use a Geissele RR. I know that Midwest Industries has an upper receiver rod with a removable top piece that fits into the charging handle groove for added stability, but I've had nothing but success with the Geissele RR.

https://www.midwestindustriesinc.com/MI-Upper-Receiver-Rod-p/mi-urr.htm

[Kswhitetails]

Nothing wrong with the RR. I’m guessing you caught them on a bad day, something every business owner should be aware of. Glad their taking care of you. Keep the horde updated. I’d be willing to bet it’s a simple fix and will be handled as it should. Marks always been a stand up guy, albeit a little slow. He does good work.

[Hansel&Grendel]

Agreed. Mark is outstanding as is his wife. Yes, a bit slow at times, but worth the wait. The barrel is already in their hands. Mid-March turnaround time.

[1075 tech]

The real point being made here is that the proper technique is to nitride the barrel first, then install, torque and time the extension/alignment pin, afterwards. Since the barrel and the extension are usually 2 separate alloys, their heating/cooling coefficients will differ and the nitriding process will cause them to loosen at times. So this guru-shop must not be as guru-good as supposed. I would strongly consider shopping elsewhere.

I have heard of this before. Improper process in the nitriding procedure.

I posted some time ago regarding a 5.56 barrel that I was having issues with. It ended up sitting in the safe for a couple of years until I finally got around to doing something with it. Using a RR, I went to remove the barrel nut and with very little effort, the barrel spun out of the extension. Barely more than hand tight.

[Wheelhorse]

I have heard of this before. Improper process in the nitriding procedure.

I posted some time ago regarding a 5.56 barrel that I was having issues with. It ended up sitting in the safe for a couple of years until I finally got around to doing something with it. Using a RR, I went to remove the barrel nut and with very little effort, the barrel spun out of the extension. Barely more than hand tight.

The way I understand this, either the pin was sheared or was too short and never was properly fitted locking the barrel and extention together. Which was it?