Broken Barrel Nut

[titsonritz]

Pictures to follow this evening.

So when I say “wrench” I mean the wrench attachment that has grooves to fit the barrel nut.

https://aeroprecisionusa.com/m4e1-ba...ut-wrench.html

According to Aero Precision, this is a pretty common problem and it’s difficult to keep the torque wrench perfectly perpendicular.

The barrel nut is this one, with all teeth broken off.

https://aeroprecisionusa.com/cop-barrel-nut.html

That should be all you need to know about Aero. This kind of shit is SOP

Oh, yeah. I looked at the Aero site, but their pics didn't give me the idea it was that recessed. This one does:

Attachment 52410

May be able to tap it, but pipe wrench definitely not an option.

I am I missing something here? It looks to me that you should be able to remove 8 screws and remove that collar (it does look integral to me) on that POS "barrel nut" then use channel locks or even pipe to remove the barrel nut.

[AKDoug]

It is integral, no removing it. Not to bust your chops ZkMZ, but you went WAY past 50 ft/lbs if you broke ALL the teeth off that nut. That makes it a bigger issue because it is torqued on there with a huge amount of force. If you have any nubs left at all, I would try a good punch and a hammer to try and work the nut off. I doubt you will be successful due to the amount of force you used to put the nut on in the first place.

The good news is, you have an upper that will likely work anyway. You won't be able to remove the barrel at any point, but so what?. It will likely function for a very long time and you can chalk this up to a learning experience.

[titsonritz]

It is integral, no removing it.

Good God, why? Great innovative improvement, probably a BS selling point about superior accuracy or some such dickery

[TMS951]

I'd get a new torque wrench before trying something like this ever again. I think your wrench reads about 100lb/ft too low.

Please be more specific on 'all the teeth are gone', I find it almost impossible that they are all gone flush. With no picture yet its hard to say.

I would use a punch or screwdriver and a mallet to try to get onto any material left and hammer it into turning.

If they really all broke flush like that I'd say that barrel nut had some issues and Aero should try fixing it for you.

[26 Inf]

Good God, why? Great innovative improvement, probably a BS selling point about superior accuracy or some such dickery

Just from what I've looked at -

It seems one advantage (a small one) is that you should be able to torque the barrel nut without worrying about timing for the gas tube.

They say it is semi-monolithic, the pressure from the forearm/tube transfers to the receiver instead of the barrel nut. I'm not an engineer, but it seems that it should function as good or nearly as good as a puredee monolothic rail in this aspect.

It also looks as if the compatible choice of handguards may be limited to Aero - which is an advantage to them if you are the cynical sort.

[26 Inf]

A couple of things I would try before I went to welding, etc.

As I understand a couple of teeth are left. Are any threads from the barrel nut visible? If you have enough surface simply use a pipe wrench to remove the barrel nut.

Since it is 'stuck' I would try to use barrel blocks first in order to ensure I didn't unseat the barrel extension. Otherwise, make sure your reaction rod is solidly secured.

You can make a set of barrel blocks easily enough -

* get two short lengths of 2x4, mate them perfectly together tighten them into your vise (alternatively you could screw them together);

* use a speedbore type ( http://www.irwin.com/tools/drill-bit...speed-bit-sets ) as close to your barrel diameter as possible and dril through the 2x4's at the joint - the speedbore screw end gets you started and holds in place until the larger cutting bit engages the wood;

Attachment 52409

You say there are a couple of teeth left on the barrel nut. If the pipe wrench won't work, drive the nut off. The receiver has to be solidly mounted for this, so I would probably use the reaction rod to reduce vibration.

If you have a piece of hardwood, I would use it against the tooth, otherwise use a large machinist punch. Make sure it is solidly mounted and that the punch/board is solidly against the tooth. Use a big enough hammer to transfer some energy and sharply rap - versus pound/beat - looking for an impact that jars with as little force as possible. You can increase the power of your blows as needed, but start with a sharp rap.

You'll get it.

It looks like we've scared old ZKMC18 off. Just in case he's reading this, I wanted to repost my suggestions of 4 days ago.

Good luck!

ETA: the reason to use a piece of hardwood if possible, is because even though a piece of oak trim or 1x2 is harder than a piece of pine, it is still softer than the metal. If the force isn't going to be enough to loosen the nut, the wood will give before the last tooth does. In theory. When faced with situations like this Mr. Alexander (my he RIP) taught us shop kiddies to try to use a sacrificial piece of material before going to the big guns.

[ZKMC18]

I appreciate everyone’s input.

I think I just had a cheap torque wrench that didn’t read the correct foot-pounds.

I ordered two more barrel nut wrenches and a breaker bar. when I say I broke “all the teeth off” I mean, at this point, after trying with three different different aero barrel nut wrenches (all of which became extremely distorted and unusable), every tooth is so worn down from pressure, the wrenches don’t make a solid connection.

I am pretty convinced it had to be over torqued and I’ll get it a go at the Range (with no one else nearby).

I will not buy Aero precision products for another build. I like the idea, but as they admit, is very difficult to keep your torque wrench or breaker bar completely perpendicular to the barrel nut. My fault but I don’t think it’s a good design.