ar15 locking lug strength?

[Shadow9mm]

Talking to a fried that had a stuck barrel nut. he has an action rod that engages the lugs in the barrel. However he was looking at getting an upper action vise.

My thinking was an action rod would be a lot stronger way to hold the barrel/receiver than an action vise as the lugs on the barrel would be a lot stronger than the receiver itself.

his concern was snapping or bending a lug.

how much force can the lugs take? I tried estimating by using the psi, rating it at half due to using the width vs the length, but the online calculators were showing over 3 million ft-lb when converted from psi... that cant be right. I feel like I am missing something.

the other consideration is the pin that keeps the barrel from rotating in the receiver. since you are basically torquing against that pin in the receiver. to get the barrel nut loose.

on a side note, he thinks the nut may have been lock-tited, which can be addressed with heat as I understand it.

 

[HiBC]

Sort of depends on what its stuck on. The barrel nut applies direct load to the barrel extension flange,clamping the flange to the face of the upper,. If the "stuction" resistance is between the barrel nut and the barrel extension flange,then the action bar is the strongest /safest bet. I would not worry about breaking off the steel locking lugs of the barrel extension.

Its a little different if the "stuction" is between the barrel nut and the upper receiver threads (that are SUPPOSED to be coated in moly grease...not loctite). If its thread on thread friction, or LocTite, the upper receiver jaw may be best.

Except if you are heating enough for a hi-temp locTite, A plastic clam on the upper may soften/melt . If that clam is made of nylon, most nylons are injected at under 500 deg f. Loctite grades vary. The hi-temp ones hold at over 400 deg f. I have no idea what grade could be there. If it went together dry,galling is a possibility. Steel galled to aluminum can be very stuck.

Too many unknowns to give a good answer. I'm confident the action bar engaging the locking lug recesses in the heat treated high strength steel of the barrel extension is very strong. If there is a weak link,its probably the notch in the upper where the index pin is.
Before you start...scribe a small witness mark between the barrel and barrel extension in case you manage to unscrew the barrel extension from the barrel.

 

[Shadow9mm]

From what I was told he got a stag upper used. It has a Hogue free float rail on it. he has the action bar in, using a strap wrench, and cannot get it to budge even with some heating from a heat gun. yes he is turning it the right direction.

 

[HiBC]

OK.
Just to suggest there is a limit to how lathered up to get, a new stripped upper can be had for what? $65?.

If he's thinking about buying another receiver tool...

that costs some.

What is he trying to achieve? A different forend? A different barrel?

Why is it coming apart? If he has a new forend,they generally come with a barrel nut. A $65 upper would give him the job of just salvaging the barrel.

Etc. A gun project gone sideways is usually a time to have a cup of coffee,breathe. Lower the intensity then make an assessment.

Has he removed the gas tube?

 

[Shadow9mm]

Reason is swapping out hand guards. Going from the Hogue free float to a light weight aluminum free float for bipod and mounting options.

the barrel is working really well for him, getting around 1/2 moa with his hand loads. regardless of what happpens the barrel nut has to come off.

 

[stagpanther]

maybe something like this?

 

[Shadow9mm]

maybe something like this?

Similar guard, but the pic he sent its the more sporterized style woth no rail or mounting holes.

As far as the wrench. He has bern using a strap wrench up to this point. He said he looked for the hogue tool but was having trouble finding one. He was considering trying a pipe wrench

 

[stagpanther]

I've used a pipe wrench on other style barrel nuts that also rely on friction to set but at which torque the strap wrench does not work. It will likely mar the finish of the hoque barrel nut--but a pipe wrench will get it off.

 

[ocharry]

my action rod has a sail on it that engages the charging slot. So it not only engages the locking lugs but the receiver as well, that way it takes the load off the indexing pin when you torque the nut. I think it is the best of both worlds, the only thing moving is the nut when you torque.

i also think if i were trying to take this thing apart i would use a solid wrench and ditch that strap wrench. they just dont give me solid feel feed back, but that is just me.

just curious what kind of wrench does the nut take to fit it?? maybe he should get the correct tool for the job??

yep a pipe wrench will get it to move...sometime a sharp wrap will help, its the shock thing or therapy..lol

i will say that if the steel is galled (as mentioned by Mr HiBC ) to the aluminum threads as it could be if not lubed correctly when installed or over torqued or some kind of hot rod thread locker was used, that it has been my experience that when and if you do get something to move it usually takes the aluminum with it.....so you could wreck the threads on the receiver

i think you should be holding the barrel and the receiver so that when you apply pressure to the nut it is the only thing moving

just some things i have learned along the way

ocharry

 

[Shadow9mm]

my action rod has a sail on it that engages the charging slot. So it not only engages the locking lugs but the receiver as well, that way it takes the load off the indexing pin when you torque the nut. I think it is the best of both worlds, the only thing moving is the nut when you torque.

i also think if i were trying to take this thing apart i would use a solid wrench and ditch that strap wrench. they just dont give me solid feel feed back, but that is just me.

just curious what kind of wrench does the nut take to fit it?? maybe he should get the correct tool for the job??

yep a pipe wrench will get it to move...sometime a sharp wrap will help, its the shock thing or therapy..lol

i will say that if the steel is galled (as mentioned by Mr HiBC ) to the aluminum threads as it could be if not lubed correctly when installed or over torqued or some kind of hot rod thread locker was used, that it has been my experience that when and if you do get something to move it usually takes the aluminum with it.....so you could wreck the threads on the receiver

i think you should be holding the barrel and the receiver so that when you apply pressure to the nut it is the only thing moving

just some things i have learned along the way

ocharry

From what he told me the factory tool was proprietary and discontinued and he was having trouble finding one.

 

[10-96]

Not trying to be smart, but he did get the gas tube out- right?

 

[Shadow9mm]

Its out in the pic he sent me, I checked too

 

[ocharry]

so Shadow.....did your friend get he barrel nut off???

curious minds want to know

ocharry

 

[Shadow9mm]

Yes it came off. He ended up having to use a pipe wrench. Could not get enough torque with his strap wrench. Said it lightly marred the barrel nut.