Ionic action between barrel nut and receiver?

[Iraq Ninja]

I have to admit I have never heard about this. But, considering the source (survivalblog), I have to wonder about it...



Front Fell Off
Ionic action between barrel nut and receiver caused failure of joint. Photo by Ranger Instructor, summer 2009.
http://i254.photobucket.com/albums/hh119/mzmadmike/guns/frontfelloff.jpg

[kmrtnsn]

I'd like to see a pic of the barrel nut.

[bkb0000]

well obviously he'd heard about it... otherwise he wouldnt have dummy-corded the FSB to the carry handle in anticipation.

WTF is "ionic action?" sounds like a toothbrush ad.

[Iraq Ninja]

Here is the source

http://www.survivalblog.com/2009/08/letter_re_the_usefulness_of_th_1.html

As you read his bio, keep in mind he was in the Air Force and did a "combat deployment" in Kuwait...

[kmrtnsn]

Hey! Show some respect! In his own words he is "THE Michael Z. Williamson. There are no others, and there are a great many people thankful for that fact.", and a renaissance faire armorer and writer of all things!

[kmrtnsn]

I was looking at the picture a bit and was noticing that the barrel extension has scoring consistent with rubbing or vibration from being loose for quite a while. In addition, there seems to be an inordinate amount of wear on the threads. I think that more likely the barrel nut cracked, the barrel worked loose a bit, then the barrel nut split in half.

[bkb0000]

A mostly dry weapon (dry teflon is preferred) will function very well, and will blow itself clean of sand with each shot--one time the direct gas impingement is very useful. Oil should be used as a repair step after extensive firing if malfunctions occur. Oily weapons will clog up, and repeated cleaning will not solve the problem, and, as many Vietnam vets will attest, can make things worse, as well as wearing out the weapon.

I dont think i trust his opinion on stuff.

i can believe the barrel nut threaded out somehow.. but i don't understand this "ionic action" shit... if it's a real thing and i've never heard of it, so be it... but "ionic" would lead me to believe from-ion, and ions are:


An ion is an atom or molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.

[Quib]

The person who took that photo, and who knows the truth behind the story, is a member of TOS.

[Quib]

I was looking at the picture a bit and was noticing that the barrel extension has scoring consistent with rubbing or vibration from being loose for quite a while. In addition, there seems to be an inordinate amount of wear on the threads. I think that more likely the barrel nut cracked, the barrel worked loose a bit, then the barrel nut split in half.

Don’t quote me on this, but if my memory serves me correctly, the owner of that picture said the soldier was issued the weapon and knew the barrel nut and barrel were loose. This was ignored long enough that through training with the weapon, the barrel separated from the upper receiver. The barrel nut being loose basically sheared away the upper receiver threads.

I don’t visit TOS anymore, but if anyone is interested in knowing the first-hand truth behind that photo I can get you the name of the individual who took it.

When that picture was posted on TOS, I asked for permission from the individual, to use the photo as an example in the forums I Moderated at that time.

[GreyOps]

I've never heard of "ionic" corrosion leading to failure of a part. There is such a thing as "galvanic" corrosion which occurs when two dissimilar metals are in electrical contact with one another. This is why large storage tanks and ship's hulls use sacrificial anodes (typically zinc) to prevent corrosion of the structure metal. Shouldn't happen with steel and aluminum.

[LOKNLOD]

Quib's explanation sounds more plausible to me.

I think what they're talking about "ionic action" is galvanic corrosion. Dissimilar metals in contact will corrode or oxidize due to transfer of electrons (creating ions) from the anodic to cathodic metal. Steel and aluminum will do this (with the aluminum suffering the damage, IIRC) but they are relatively close on the galvanic series so it could be worse. It really needs moisture in there to assist to see it act most vigorously.

The big reason to avoid graphite-based greases for the barrel nut is that graphite is at the far end of the galvanic series (the cathodic end) and could cause both of the metals to corrode. Personal take: when it's in a grease that keeps moisture sealed out it's probably not the end of the world, but it doesn't hurt to avoid it, either.

Surface finishes play a role too and I believe that the anodization of the Aluminum assists in protecting the aluminum. Not sure if the parkerization of the steel helps any.

[Heavy Metal]

When I see a rifle like that, my first question was how many times has it been jumped with?

[thopkins22]

I think what they're talking about "ionic action" is galvanic corrosion. Dissimilar metals in contact will corrode or oxidize due to transfer of electrons (creating ions) from the anodic to cathodic metal. Steel and aluminum will do this (with the aluminum suffering the damage, IIRC) but they are relatively close on the galvanic series so it could be worse. It really needs moisture in there to assist to see it act most vigorously.

This is correct. For a long time I was considering building a steel sailboat. Talking to builders about aluminum boats convinced me that steel was the way to go, as there are many steps required to keep all the steel parts from touching the aluminum hull. It does not take long at all for the aluminum to be totally destroyed when touching steel in a saltwater environment.

I had never heard of it being an issue on ARs, probably because they don't live their lives floating in saltwater.

[kennith13]

Every restorer of vehicles with aluminum bodies has dealt with this before. The metal is just eaten away on early designs without good isolation. The steel rots to pieces, and the aluminum turns to dust. It's the same with boats, as well. As a matter of fact, the whole sacrificial anode thing is a way to use this effect to help prevent the corrosion in the first place.

A direct relation to the AR platform is an aluminum block engine. Without proper preparation and care, the removal of a steel bolt from a threaded aluminum block will reveal wanton horrors of chemistry happening right under your nose. If you are lucky, the bolt will snap in two. If you are unlucky, the aluminum threads will come out with the bolt, which will snap in two right at the end.

It's a result of that same corrosion.

Does it happen to ARs? Sure. I'm not aware, however, that it happens fast enough to cause any problems. As well, better steel and aluminum helps prevent this from happening so readily, and firearms are made of better stuff than mass sourced bolts and sand cast aluminum engine blocks.

I do know that I make darn sure to use the proper grease when assembling this connection, and I do my very best to keep from scratching off too much of the coatings on the parts in this area. Some of these coatings have their own corrosion inhibiting properties, even if they are no longer present in the area of concern.

Is it possible that such corrosion caused a failure of the threads in his AR? Yes. I doubt it, though. I'd guess that there were other contributing factors.

[spr1]

The phenomena described, and postulated to be the causal factor, is actually Galvanic Corrosion, as noted in the table below. I would however first suspect a loose barrel nut and the associated loss of preload in the threaded connection. There are fairly significant loads from the bolt running back and forth, and without that connection clamped/preloaded to a high enough value, the relatively soft Aluminum will fail in fairly short order.

Galvanic Table
The following galvanic table lists metals in the order of their relative activity in seawater environment. The list begins with the more active (anodic) metal and proceeds down the to the least active (cathodic) metal of the galvanic series. A "galvanic series" applies to a particular electrolyte solution, hence for each specific solution which is expected to be encountered for actual use, a different order or series will ensue. In a galvanic couple, the metal higher in the series (or the smaller) represents the anode, and will corrode preferentially in the environment. Listed below is the latest galvanic table from MIL-STD-889 where the materials have been numbered for discussion of characteristics. However, for any combination of dissimilar metals, the metal with the lower number will act as an anode and will corrode preferentially. The table is the galvanic series of metals in sea water from Army Missile Command Report RS-TR-67-11, "Practical Galvanic Series." (reference)

Active (Anodic)

Magnesium
Mg alloy AZ-31B
Mg alloy HK-31A
Zinc (hot-dip, die cast, or plated)
Beryllium (hot pressed)
Al 7072 clad on 7075
Al 2014-T3
Al 1160-H14
Al 7079-T6
Cadmium (plated)
Uranium
Al 218 (die cast)
Al 5052-0
Al 5052-H12
Al 5456-0, H353
Al 5052-H32
Al 1100-0
Al 3003-H25
Al 6061-T6
Al A360 (die cast)
Al 7075-T6
Al 6061-0
Indium
Al 2014-0
Al 2024-T4
Al 5052-H16
Tin (plated)
Stainless steel 430 (active)
Lead
Steel 1010
Iron (cast)
Stainless steel 410 (active)
Copper (plated, cast, or wrought)
Nickel (plated)
Chromium (Plated)
Tantalum
AM350 (active)
Stainless steel 310 (active)
Stainless steel 301 (active)
Stainless steel 304 (active)
Stainless steel 430 (active)
Stainless steel 410 (active)
Stainless steel 17-7PH (active)
Tungsten
Niobium (columbium) 1% Zr
Brass, Yellow, 268
Uranium 8% Mo
Brass, Naval, 464
Yellow Brass
Muntz Metal 280
Brass (plated)
Nickel-silver (18% Ni)
Stainless steel 316L (active)
Bronze 220
Copper 110
Red Brass
Stainless steel 347 (active)
Molybdenum, Commercial pure
Copper-nickel 715
Admiralty brass
Stainless steel 202 (active)
Bronze, Phosphor 534 (B-1)
Monel 400
Stainless steel 201 (active)
Carpenter 20 (active)
Stainless steel 321 (active)
Stainless steel 316 (active)
Stainless steel 309 (active)
Stainless steel 17-7PH (passive)
Silicone Bronze 655
Stainless steel 304 (passive)
Stainless steel 301 (passive)
Stainless steel 321 (passive)
Stainless steel 201 (passive)
Stainless steel 286 (passive)
Stainless steel 316L (passive)
AM355 (active)
Stainless steel 202 (passive)
Carpenter 20 (passive)
AM355 (passive)
A286 (passive)
Titanium 5A1, 2.5 Sn
Titanium 13V, 11Cr, 3Al (annealed)
Titanium 6Al, 4V (solution treated and aged)
Titanium 6Al, 4V (anneal)
Titanium 8Mn
Titanium 13V, 11Cr 3Al (solution heat treated and aged)
Titanium 75A
AM350 (passive)
Silver
Gold
Graphite
End - Noble (Less Active, Cathodic)

[kmrtnsn]

I am not a metallurgist, nor do I play one on T.V. but I don't think corrosion of any type is the issue here. Look at the picture. There is vibration/friction wear on the barrel extension, it was moving around so much so that the parkerizing is gone. That is indicative of the barrel moving back and forth minutely over a long period of time; the barrel nut was either quite loose, or cracked. Look at the threads on the upper receiver, they are aluminium, the barrel nut is steel. The threads are pretty much intact, not missing, not corroded away. They are missing quite a bit more finish than I would expect from taking the barrel nut on and off with a wrench. I want to see the barrel nut, I think it is key to this whole deal. I would venture to guess that it is in two pieces.

[Quib]

Found the thread, compliments of “Bing” web search.

Here are the exact chain of events........http://www.ar15.com/forums/topic.html?b=3&f=118&t=449676

[SV650Squid]

Don’t quote me on this, but if my memory serves me correctly, the owner of that picture said the soldier was issued the weapon and knew the barrel nut and barrel were loose. This was ignored long enough that through training with the weapon, the barrel separated from the upper receiver. The barrel nut being loose basically sheared away the upper receiver threads.

I don’t visit TOS anymore, but if anyone is interested in knowing the first-hand truth behind that photo I can get you the name of the individual who took it.

When that picture was posted on TOS, I asked for permission from the individual, to use the photo as an example in the forums I Moderated at that time.

IIRC, the Specialist that is in that pic ended up doing a shitload of flutter kicks and his M-4 was replaced with an M240 for the rest of Ranger School. He admitted that it was loose for at least 3 DAYS before "front fell off."

[geminidglocker]

IIRC, the Specialist that is in that pic ended up doing a shitload of flutter kicks and his M-4 was replaced with an M240 for the rest of Ranger School. He admitted that it was loose for at least 3 DAYS before "front fell off."

Yeah, that assclown belongs in the front leaning rest permanantly. How exactly does one do a combat deployment to Kuwait? We accidentally killed a Kuwaity national before we even entered Iraq. Apparently only like 15-20% of the inhabitants of Kuwait are native, the rest just work for them. It was an accident but still had repercussions. Kuwait is a peaceful area last time I was there. A shithole all the same, but "Combat" I don't think so.
Oh, and yeah, why was it 550 corded together anyway, they should have used duct tape.

[5pins]

Oh, and yeah, why was it 550 corded together anyway, they should have used duct tape.

To secure a barrel properly a combination of 500mph tape and para cored is called for.

[SV650Squid]

To secure a barrel properly a combination of 500mph tape and para cored is called for.

According to the OP from TOS (who's the ranger school instructor that took the pic) EVERYTHING is dummy-corded at the school.

[Heavy Metal]

Looks more like moronic action than ionic.

[Jim D]

I got issued a M4 with a loose bbl nut (gas tube rattled from side to side on the upper). Had two DS's tell me it wasn't an issue. Once my Aimpoint shit the bed and I had to take it down to the Armorer...both the M4 and CCO were replaced.

I bet if I'd have shot that thing for a while, something like that might have happened.

[Armati]

Utter nonsense. Galvanic corrosion is real but I have never heard of it in AR's. There are no Army Technical Bulletins on it. There is a bulletin about not using Simple Green or other ammonia based products on aluminum.

In this case, bad maintenance is at fault. I am sure Ranger School M4's get the shit beat out of them and most of the weapons have been 'studentized.' Checking a loose barrel is suppose to be a biannual check done by a 45B.

The first thing that will happen is accuracy will go south. Many will misdiagnose this as throat erosion / barrel wear.

[Thomas M-4]

Some body got Smoked!!