Aero precision m5e1 with JP barrel issue

[Gasman 15]

Hi All,

I'm doing my first 308 build. I am building an Aero Precision m5e1 with a JP 18 inch light contour 1:11.25 twist barrel and JP BCG.
The issue I am having is that when I install the barrel hand tight the BCG will go into battery. However, When I torque the barrel nut to 40 ft lbs the BCG will no longer go into battery. I think when I torque it the barrel is rotating just enough to prevent the bolt from going into battery. Has anyone had this problem? If so, do you have a solution. I've never had this with an AR 15.

Thanks

 

[flyer]

How are you torquing it?

 

[bigjake83]

Hi All,

I'm doing my first 308 build. I am building an Aero Precision m5e1 with a JP 18 inch light contour 1:11.25 twist barrel and JP BCG.
The issue I am having is that when I install the barrel hand tight the BCG will go into battery. However, When I torque the barrel nut to 40 ft lbs the BCG will no longer go into battery. I think when I torque it the barrel is rotating just enough to prevent the bolt from going into battery. Has anyone had this problem? If so, do you have a solution. I've never had this with an AR 15.

Thanks

Either way it sounds like the upper is out of spec. I would send the upper back.

 

[Gasman 15]

How are you torquing it?

 

[hlee]

Pics of the bcg with the barrel nut hand tight and torqued?

 

[flyer]

I think the key is probably the barrel extension pin and the slot in the upper.

The clamp you are using seems a bit weird to me. I've used one that clamps the rail but not one that relies on squeezing the receiver top to bottom to resist the torque. I would try just using the rail side and grip it high in the vice with the receiver upside down instead of sideways.

Another thing you can do is get the barrel nut hand tight and the BCG locking up, then create a witness mark between the barrel extension and upper inside the receiver. If torquing the barrel nut moves the extension relative to the receiver, you have to figure out what is letting it do that, that could be the upper or the barrel.

If the barrel extension is not moving, I can't think of what is going wrong without seeing it myself.

 

[Gasman 15]

That’s a good idea. I’m going to try the witness marks to make sure it is the Barrel turning. Has anyone used Brownells barrel extension torquing tool? Good, bad?

 

[flyer]

Those are some times called reaction rods, I've never seen it happen but I hear the friction from barrel nut to receiver can cause the barrel extension pin to shear or mess up the receiver, caution is advised with those.

 

[Gasman 15]

I heard that too. That’s why I haven’t tried one. I’m going to send a picture hand tight and torqued. It almost seems like the barrel extension is just the slightest bit to deep. Like the indexing groove is too deep.

 

[Gasman 15]

After dialing down I was able to get to get to battery at 37 ft LBs of torque. I think beyond that I’m stressing the receiver. Any thoughts on that?

 

[bigjake83]

After dialing down I was able to get to get to battery at 37 ft LBs of torque. I think beyond that I’m stressing the receiver. Any thoughts on that?

If you can not go into Full Battery past 37 FT Lbs, your Upper is fucked! You should be able to tighten your Barrel Nut 45-70 FT Lbs on a Large Frame AR, and have 0 issues closing your bolt.

Send the upper back or buy a new one, before you hurt yourself or someone else.

 

[Gasman 15]

Thanks for the advice. I’m going to call Aero. The lower is phenomenal. I think I will not put a live round in until I can get it to 45

 

[.30kal]

It’s the upper that is out of spec, specifically the slot where the pin on the barrel extension slides in. I had the same issue with an Aero M4E1. They should exchange it.

 

[chopit]

I have had that same problem with 2 aero m5 uppers and a friend at work also same issue. I used the brownells reaction rod and was able to finally get my torque.

 

[flyer]

If you can not go into Full Battery past 37 FT Lbs, your Upper is fucked! You should be able to tighten your Barrel Nut 45-70 FT Lbs on a Large Frame AR, and have 0 issues closing your bolt.

Send the upper back or buy a new one, before you hurt yourself or someone else.

Actually in an AR the barrel (nut) threads don't do anything beside retain the barrel in the upper, all of the force from firing is contained between the barrel chamber, barrel extension and bolt. A loose barrel nut might make an AR inaccurate or unreliable but not really dangerous.

The actual barrel nut torque spec is probably more about keeping it tight while undergoing heat cycling than having a certain amount of load retaining the barrel in the upper.

So what happens when you exceed 37 ft-lbs?

If you can see something changing, can you tell which piece is allowing it?

Edited to insert a word I missed.

 

[RifleBlog]

Your upper is probably fine.

Torque values on that wrench are linear, so when you add an extension and angle (90 degrees and about 3” extension).....37 ft/lb becomes 45 ft/lb.

 

[Gasman 15]

I’m actually do 2 identical builds. I finished the second one today with no issues. I’m going to send the receiver back. The second one has zero rotational play from barrel to receiver and torqued right up to 55 with no problem.
Thanks for the help everyone

 

[bigjake83]

I’m actually do 2 identical builds. I finished the second one today with no issues. I’m going to send the receiver back. The second one has zero rotational play from barrel to receiver and torqued right up to 55 with no problem.
Thanks for the help everyone

Make sure you season the treades, use anti seize on the threads of the upper receiver and red Loctite on the Barrel Extension/upper receiver.

If you're not sure about what I'm talking about send me a PM.

 

[bigjake83]

Your upper is probably fine.

Torque values on that wrench are linear, so when you add an extension and angle (90 degrees and about 3” extension).....37 ft/lb becomes 45 ft/lb.

WRONG!

 

[bigjake83]

Actually in an AR the barrel threads don't do anything beside retain the barrel in the upper, all of the force from firing is contained between the barrel chamber, barrel extension and bolt. A loose barrel nut might make an AR inaccurate or unreliable but not really dangerous.

The actual barrel nut torque spec is probably more about keeping it tight while undergoing heat cycling than having a certain amount of load retaining the barrel in the upper.

First of all...there are NO! Barrel threads besides one use to install the barrel extension, barrels do not thread into an upper receiver!!!

We are not talking about a loose barrel nut here, when he applies proper torque to the barrel nut it's causing it to not go into full battery and that is a big fucking safety issue!!

And to No Surprise wrong again on your last statement! The barrel nut soul purpose is to hold the Barrel in place in the upper receiver at a proper torque spec.

Flyer..


Every time you come on to the semi auto form you put out Incorrect and dangerous information, stay the FUCK out of here before you get somebody Hurt.

 

[Gasman 15]

Make sure you season the treades, use anti seize on the threads of the upper receiver and red Loctite on the Barrel Extension/upper receiver.

If you're not sure about what I'm talking about send me a PM.

I did not use red loctite but I did season the threads and used anti seize on the threads. I'm planning on going out to the range to do a systems check and test fire before I loctite anything.
Thanks for the help

 

[bigjake83]

I did not use red loctite but I did season the threads and used anti seize on the threads. I'm planning on going out to the range to do a systems check and test fire before I loctite anything.
Thanks for the help

No worries... Be Safe

 

[flyer]

First of all...there are NO! Barrel threads besides one use to install the barrel extension, barrels do not thread into an upper receiver!!!

We are not talking about a loose barrel nut here, when he applies proper torque to the barrel nut it's causing it to not go into full battery and that is a big fucking safety issue!!

And to No Surprise wrong again on your last statement! The barrel nut soul purpose is to hold the Barrel in place in the upper receiver at a proper torque spec.

Flyer..


Every time you come on to the semi auto form you put out Incorrect and dangerous information, stay the FUCK out of here before you get somebody Hurt.

Sorry I forgot the word nut in barrel nut threads.

The rest of my post is correct.

Nothing bad happens if your barrel nut loosens up unless you keep firing it so much that the bolt lugs break but even that is much more likely to make the gun stop running than anything else.

Take a little time to learn about the platform and think about the forces acting on the action. The upper and lower mostly just locate things which is why both AR uppers and lowers have been somewhat successfully made out of plastic.

To reiterate, loose barrel nuts are not good but they are not catastrophic. Nothing I've said is dangerous.

 

[bigjake83]

Sorry I forgot the word nut in barrel nut threads.

The rest of my post is correct.

Nothing bad happens if your barrel nut loosens up unless you keep firing it so much that the bolt lugs break but even that is much more likely to make the gun stop running than anything else.

Take a little time to learn about the platform and think about the forces acting on the action. The upper and lower mostly just locate things which is why both AR uppers and lowers have been somewhat successfully made out of plastic.

To reiterate, loose barrel nuts are not good but they are not catastrophic. Nothing I've said is dangerous.

Again...WE ARE NOT TALKING ABOUT A LOOSE BARREL NUT!!!

we are talking about the OP not even being able to apply sufficient amount of torque without it contorting the UPPER FUCKING receiver, thus causing the OP's BCG to not go in and out of Battery properly.

And there is NO Plastic Upper Receivers... From the face of the receiver half way down, is still Aluminum with overmolded polymer.

 

[flyer]

No, we are talking about torquing a barrel nut to 37 ft-lbs instead of 50+ and he's worried that 37 isn't enough.

If it doesn't loosen, 37 ft-lbs is fine.

If it loosens, it's not going to blow up.

I don't know who scared you so much about barrel nut torque but it's an irrational fear.

You've got to really try to blow up an AR and the things that will do it are really bad headspace, shooting .300 Blackout through a 5.56 barrel or something equally stupid.

Unless your barrel extension is spinning relative to the barrel, there is not much you can do in assembly that will be dangerous if your headspace is good and your BCG won't fire out of battery.

The AR BCG is intended to prevent out of battery firing by design so it doesn't happen without super crappy or defective parts.

 

[10ring1]

Off OP's topic but pertinent to the convo: I would tend to think that if the barrel nut was not completely tightened and started to loosen, the headspace would be a variable at that point becoming dangerous

 

[flyer]

Nope, barrel nut does not change headspace, it's purely the barrel, barrel extension and bolt.

 

[RifleBlog]

WRONG!

Such an informative post, thanks for all your extensive research and strong counterpoints in your lengthy reply.

 

[padom]

Nope, barrel nut does not change headspace, it's purely the barrel, barrel extension and bolt.

This is incorrect actually. If your barrel nut is loose enough allowing the barrel extension shoulder to move away from the face of the receiver it would change headspace. The barrel nut locks the barrel extension collar against the receiver face. The inside of the collar is against the receiver face, the outside of the collar is what the barrel nut pushes against. If your barrel extension moves away from the receiver face the headspace changes. This is very easy to test. Take your NO-GO headspace gauge, put it in your bolt and close the BCG, inserting the gauge into the barrel chamber which shouldnt close all the way. now start pulling your barrel out of the upper. Your BCG will close because you just changed the headspace.

Now, does 37ft lb vs 50ft lb change headspace. No. But a "loose" enough barrel nut surely could. Making a blanket statement that a barrel not does not change headspace is incorrect.

Long story short, his upper isnt right and needs to be replaced.

 

[flyer]

You should think about that a little more.

You know how when you buy a barrel and want it headspaced to your bolt, the barrel maker doesn't ask for your upper to do the job...

If your barrel nut is super loose and the barrel is pulling out of the upper, your bolt might not reach far enough forward to lock up in the extension but if the bolt can't twist shut the carrier won't be able to go all the way forward and the firing pin is not long enough to strike the primer in that condition.

In that case your AR doesn't run and the problem should have been addressed long before the barrel nut got that loose but headspace did not change at all.

An AR just isn't like a Savage bolt action.

 

[padom]

You should think about that a little more.

You know how when you buy a barrel and want it headspaced to your bolt, the barrel maker doesn't ask for your upper to do the job...
They dont need your upper because an AR15 barrel extension length is standard Same for every AR15 upper.

If your barrel nut is super loose and the barrel is pulling out of the upper, your bolt might not reach far enough forward to lock up in the extension but if the bolt can't twist shut the carrier won't be able to go all the way forward and the firing pin is not long enough to strike the primer in that condition.
This is correct, but we werent talking about firing pin causing ignition, we were simply talking about headspace. The fact is, as I mentioned, headspace changes. Nowhere did I say anything about a round igniting or not.

In that case your AR doesn't run and the problem should have been addressed long before the barrel nut got that loose but headspace did not change at all.
We arent talking about if it should run or not. We are talking about your blanket statement that a barrel not cannot change headspace. That is in fact incorrect. Barrel pulls out some because of a loose nut, headspace changed. You mention it above, if the bolt cant engage the lugs, or firing pin isn't igniting the round, headspace changed!

An AR just isn't like a Savage bolt action.

Dont quit your day job bud

 

[flyer]

You don't understand headspace.

You don't have headspace unless the bolt is locked up.

If your bolt doesn't go far forward enough to lock up, that's a different problem. Headspace hasn't changed if you're still dealing with the same barrel, barrel extension and bolt.

The only exception to that is if your barrel extension loosens up on your barrel which it shouldn't because it's pinned.

You should try to keep your boss happy.

 

[bigjake83]

 

[padom]

You don't understand headspace.

You don't have headspace unless the bolt is locked up.

If your bolt doesn't go far forward enough to lock up, that's a different problem. Headspace hasn't changed if you're still dealing with the same barrel, barrel extension and bolt.

The only exception to that is if your barrel extension loosens up on your barrel which it shouldn't because it's pinned.

You should try to keep your boss happy.

I am the boss. There's no point wasting anymore time with you.

 

[flyer]

I'll continue to be generous with my time (and correct).

 

[Gasman 15]

My intention was not to start a conversation on what is or is not dangerous when it comes to building ARs. It was simply because this was my first and second 308 build. I learned a lot and researched a lot including getting advice here. I can tell you that building 15s is much less complicated than 10s. Obviously we all know that DPMS and Armalite only have some compatible parts, but also tolerances in receivers seems to be much tighter on 10s. I may be wrong.

 

[flyer]

Yeah, it's really not more complicated, just easier to run in to parts that aren't quite right for each other because the standards are not really as standard as an AR15.

As for the safety discussion, you should know what can go wrong when you're building an AR but when you learn that you'll see a lot of stuff that can't go wrong unless you have a very obvious and specific problem.

I'm a geek, I've been fooling around and gunsmithing 1911s since the early 90s, then started messing with Glocks (because they are cheaper), then M1 Garands, FALs, ARs and AKs. One of these days I'm going to get around to finishing my 1919 kit...

When you geek out like that, and really look at the interaction of the parts, you can get a good appreciation for the design and find a bunch of features you would miss if you didn't know they were there.

 

[Gasman 15]

New receiver will be coming soon. If this works out, I will be a big fan of Aero.

 

[chopit]

Aero is going to swap out your upper?

 

[Gasman 15]

Yes

 

[bigjake83]

Yes

Awesome...

How's the other Upper coming along?

 

[Gasman 15]

Awesome...

How's the other Upper coming along?

Have not run any live rounds through it, but it seems to cycle great. Aero makes quality receivers. I think I may have just got one that’s slightly out of spec.

 

[Gasman 15]

Have not run any live rounds through it, but it seems to cycle great. Aero makes quality receivers. I think I may have just got one that’s slightly out of spec.

Lowers are fantastic and very easy to assemble. I’m using Timney 4lb triggers and magpul PRS stocks. I’m excited to get these things going.

 

[spife7980]

I too don’t see how a loose barrel nut could change the headspace. The headspace is set by the bolt and the barrel in relation to one another, where those two are in relation to the rest of the rifle shouldn’t really matter. If it did then how can I check my headspace with the barrel not installed on the rifle? If it did then how can you swap them to another upper and it still works out?

If the nut backs out enough so that the bolt can’t lock up that’s not really the headspace that changes. It’s just the barrel not being all the way installed. And if the bolt locks up it can’t go fire.

Where am I not understanding? Because so far I don’t see where flyer is wrong and I don’t see anyone providing any contrary information other than calling him a retard. Come on guys, prove him wrong with information instead of clamming up.

 

[10ring1]

I tend to think if the barrel nut is loose and the barrel slips out of the receiver even by .001" , say if by sheer inertia of the bolt slamming forward (after lockup and before firing, the entire chamber moves forward and the headspace is going to be longer. I may be thinking about it wrong but i am trying to explain something that is making sense to me. But maybe I am wrong too. Regardless it sounds like a dangerous proposition.

 

[padom]

I tend to think if the barrel nut is loose and the barrel slips out of the receiver even by .001" , say if by sheer inertia of the bolt slamming forward (after lockup and before firing, the entire chamber moves forward and the headspace is going to be longer. I may be thinking about it wrong but i am trying to explain something that is making sense to me. But maybe I am wrong too. Regardless it sounds like a dangerous proposition.

Exactly. Re read my above posts. Nowhere did I say how much it would change but yes it changes.

If I had the time I would make you a video with a NO GO gauge. You can go test it yourself

 

[flyer]

This is how an AR bolt locks up (without the receiver in the way).

You can see that the bolt carrier is butted up against the barrel extension and the bolt is cammed over but the bolt hasn't bottomed in the cam pin slot.

As hard as the bolt carrier can push forward, there is nothing beside inertia of the bolt forcing the bolt against the case and when the primer ignites, the case is going to push the bolt back until it is stopped by the barrel extension lugs (which is the headspace).

The barrel nut torque isn't involved.

 

[10ring1]

@flyer, so you're saying there isn't not even .001 of play when your bolt is locked up (in fire position) like u have it in the pic? I'm guessing there is

 

[10ring1]

And if there isn't the bolt head would bind and not rotate. Therefore the barrel must remain stationary and the bolt must work and be responsible for movement

 

[srt-4_uk]

Is this about .001 causing an unsafe condition or are we arguing semantics?
Fwiw, JP provides a headspace bolt with their barrels. It's just the bolt though, no upper or carrier.