Be an informed consumer!

[LRRPF52]

Because this extension appears to be through hardened-at least on the edge of the feed ramps, like I said above in 3 separate posts now. It's interesting that you chose to post in response to this, given the origin of the barrel in question.

AD500112 "Materials for Small Arms Gun Barrels" discusses much of it. There are also reports from the 1950's-1970's done by DOD and specific research labs, ranging from improving machinegun barrels, to Stelite lined barrels, different alloys and Chrome plating processes, plating and deposition techniques, and the things we see advertised today as "new and improved".

The reality is, if there is an improved method for making barrels last, several research labs with significant funding have done extensive testing on them and other methods. If a product can exhibit enough improved performance over what they are using now, the military will be all over it due to the costs associated with machine gun barrels, as well as service life on carbines. There are probably a dozen studies that won't be unclassified for a few decades on this, since DOD doesn't want technical information shared in the open, potentially falling into the hands of small arms manufacturers whose products we will have to face someday.

As to us as consumers, would you have serious reservations about pulling the trigger on a barrel that has an extension as described, where the feed ramp lip shattered like glass?

[constructor]

This is something anyone can do. Take a barrel extension that looks like stainless( they aren't they are untreated 8620), you can buy them anywhere. Stick them in a machine vice squeezing side to side and tighten the vice. WEAR GLASSES. Then take a melonited extension and do the same thing. See which one folds up and which one shatters first. What do you do if the ones many use shatter and the Melonited ones do not? Remember in the post above where I said Meloniting already hard extensions will LOWER the hardness by 1-5 points?
You see Paul I know you have an agenda. Let everyone else do the test and see what happens. I'll post some photos tomorrow.

What is the topic here? "Be an informed consumer " Maybe it should be "don't believe the BS find the facts on your own"
Rifling, cone angle and engraving force tests-
http://www.dtic.mil/dtic/tr/fulltext/u2/a431357.pdf


Fairly easy to ask an engineer what would happen to a piece of 8620 that had been hardened before when subjected to the Melonite process.
Burlington- (714) 921-4045
Bodycote-Phone262) 782-5553
Parker trutec- Phone870) 236-6920

This is what your report says on page 6-Pretty much all it says about Nitriding. Stainless wasn't even considered for a material to make barrels from.
They were looking for an improvement to 4150 and seems like they couldn't find one...especially since we are still using 4150 today.
Pretty tough read since it looks like it was copied back in the 60s

"I U)Test on nitrided barrels indicate improvements over untreated barrels but not as great as those due to chromium plating."

[constructor]

Notice Melonite and similar treatments were not used until the 80s. It's pretty tough to test it in the 60s if it did not exist until the 80s.
Carburizing pushes the hardness deeper into the metal than Melonite, if anything caused it to be brittle it was the carburizing that is harder and deeper.
Still haven't seen any photos, I don't think it happened.


Saturday, August 7, 2010
Metal Treatments: Ferritic Nitrocarburizing/Melonite/Tenifer
In the last few posts, we looked into metal treatments like plating, parkerizing and bluing. In this post, we will study a newer form of metal treatment that has rapidly gained popularity in the firearms industry since the 80s. This metal treatment process is called Ferritic Nitrocarburizing, but there are several variants of this. The most popular variants are known by their trademarked names of Tenifer and Melonite and the main difference between these two are the chemicals used during the process. Both these trademarks, along with Tufftride, are owned by the same company, Degussa of Germany. The Degussa website explains that Tenifer and Tufftride are actually the same process and the only reason for the different names is because they couldn't get the trademark Tenifer registered in all countries and therefore use Tufftride in the countries where they couldn't get the name Tenifer registered.

To understand this method, we must first understand a few basic properties of iron and steel. Some materials, such as iron and steel, can exist with different crystalline structures. These different crystalline structures cause the same material to have different physical properties (e.g. different hardness, elasticity etc.). These different crystal structures are called "phases". Examples of such phases are: ferritic phase, austenitic phase, martensitic phase, ledeburite phase, pearlite phase etc. Both iron and steel can be switched from one phase to another by heating to different temperatures and adding other elements and cooling at different rates to change the crystalline structure of the product. The diagram below illustrates the temperatures and carbon content % that cause steel to change from one phase to another.
Steel Phase Diagram
Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License by Christopher Dang Ngoc Chan.

The basic concept behind the Ferritic Nitrocarburizing method is to introduce nitrogen and carbon to the steel when its crystal structure is still in the Ferritic phase. The temperature when this is done ranges from between 525-650 degrees centigrade. The first Ferritic Nitrocarburizing treatment process was invented by UK chemical giant, Imperial Chemical Laboratories (ICL), who came up with a process of dropping the workpiece in a sulfur salt bath at 550 degrees centigrade. This process was called Sulfinuz treatment because of the sulfur salt content. It was mainly used for cutting tools and high speed spindle parts, but it had problems with cleaning the solution off.

Degussa of Germany came up with a more environment friendly salt-bath process, which they called Tenifer in most of Europe and Tufftride in England and Asia. They later improved on this by inventing an ion nitriding process in the early 1980s. The ion nitriding process was faster and more precise to control. As far as the firearms industry is concerned though, the processes used for metal treatment use the salt-bath. Tenifer and Melonite use the same process, but slightly different chemicals and temperatures. Melonite treatment is known to be the simpler of the processes. The process starts by creating a salt bath of alkali cyanate in a steel vessel. The steel vessel has a pipe that creates bubbles and aerates the salt bath. The workpiece is introduced into the bath and the cyanate reacts with the workpiece to form an alkali carbonate. The bath is then treated with a regenerator chemical to convert the carbonate back to a cyanate. This causes two layers to form on the surface: the compound layer and the diffusion layer. The compound layer has iron, nitrogen and oxygen and is resistant to abrasion and wear. The diffusion layer has nitrides and carbides and provides extra hardness. The end result is a corrosion resistant finish that is extremely hard and corrosion resistant.

The Tenifer process was traditionally used in the German automotive industry for years, by manufacturers such as BMW and Mercedes. Glock GmBH, which was then an unknown Austrian manufacturer, was the first to use it in the firearms industry in the 1980s. All Glock pistols come with Tenifer treatment and it became well known to the firearms industry because of their success. It is now used by other manufacturers as well, such as Steyr, Walther, Heckler & Koch etc. It is renowned for its hardness and toughness. Tenifer has a dull-gray color and has a hardness of 64 HRC on the Rockwell scale, which is very hard, considering that diamond has a hardness of 70 HRC. Tenifer is also extremely corrosion resistant and is at least 85% more corrosion resistant that hard chrome plating and almost completely salt-water resistant as well. It also has excellent anti-friction properties. Glock generally applies a tenifer coat of 0.5 mm thickness to the slides and barrels of their pistols. The slides are further subject to parkerizing treatment on top of that. So, even if the parkerized finish were to wear off, the slide is still protected by the Tenifer layer.

[LRRPF52]

I had an engineer already look at the extension. He said it appears to be through-hardened at the thin area of the feed ramps. He's not a construction engineer either, but a ME with specialty in advanced alloys, super metals, and has a very intimate knowledge of firearms specific steels, treatments, and so forth.

We already know about nitrocarburizing, Melonite, QPQ, and other surface treatment methods. The legitimate question is, does the shop sending parts out for nitriding know what to spec, how to check quality and adherence to standards, or are they just calling it good and shipping product?

Judging from what I'm seeing, it's the latter in many cases. Not sure why you keep calling me out by name, or claiming I have an agenda, but your insertion of drama into the thread is interesting, especially since I just got off the phone with Burlington and spoke with one of their engineers for over half an hour about this.

He said if the shop that made the 8620 barrel extension didn't know it was going to be nitrocarburized, he needs to know what it was tempered to. He also said that the diffusion of nitride will go deep enough into the substrate, to the point that any acute angles on a steel part can experience some degree of through hardening, which is exactly what I think happened with this extension I have.

He also said that he deals with AR15 barrel makers that do both methods. Some are concerned enough about the extensions that they send the barrels without them, while others send them assembled. The theory is that there is cause to worry about salt bath liquid residue getting into the threads, then solidifying and expanding at ambient temperature. That said, he has never seen it become an issue in practice, and has not heard any complaints to that effect.

The end story is that shops need to know what they are doing, maintain a tight series of controls over their parts sourcing, and be able to inspect critical parts for dimensional uniformity, surface condition, and maybe even consider some more extensive testing protocols.

With companies like BCM, I know we are getting that.

[constructor]

I had an engineer already look at the extension. He said it appears to be through-hardened at the thin area of the feed ramps. He's not a construction engineer either, but a ME with specialty in advanced alloys, super metals, and has a very intimate knowledge of firearms specific steels, treatments, and so forth.

We already know about nitrocarburizing, Melonite, QPQ, and other surface treatment methods. The legitimate question is, does the shop sending parts out for nitriding know what to spec, how to check quality and adherence to standards, or are they just calling it good and shipping product?

Judging from what I'm seeing, it's the latter in many cases. Not sure why you keep calling me out by name, or claiming I have an agenda, but your insertion of drama into the thread is interesting, especially since I just got off the phone with Burlington and spoke with one of their engineers for over half an hour about this.

He said if the shop that made the 8620 barrel extension didn't know it was going to be nitrocarburized, he needs to know what it was tempered to. He also said that the diffusion of nitride will go deep enough into the substrate, to the point that any acute angles on a steel part can experience some degree of through hardening, which is exactly what I think happened with this extension I have.

He also said that he deals with AR15 barrel makers that do both methods. Some are concerned enough about the extensions that they send the barrels without them, while others send them assembled. The theory is that there is cause to worry about salt bath liquid residue getting into the threads, then solidifying and expanding at ambient temperature. That said, he has never seen it become an issue in practice, and has not heard any complaints to that effect.

The end story is that shops need to know what they are doing, maintain a tight series of controls over their parts sourcing, and be able to inspect critical parts for dimensional uniformity, surface condition, and maybe even consider some more extensive testing protocols.

With companies like BCM, I know we are getting that.

" I was polishing the feed ramps on one such barrel the other day, and the thin edge of the feed ramp literally shattered off like glass"

And you have already taken it to an engineer.

Do you think I didn't talk to all of these guys 6 years ago before we sent the first parts out? From the lab test we ran barrel extensions purchased off the shelf will shatter before the same brand of extensions that have been Melonite treated. Melonite treating makes the material softer and more ductile. Like I said anyone can stick one in a vice and figure that out in a minute.

I agree with the TDP, no problem at all. Should we all buy nothing but Colt and FN parts? Companies like BCM source their parts from several places. I know some of their carriers are made by Microbest who also makes carriers for Colt and FN.
Unhardened NiB is only around 53 rockwell IIRC, hardened NiB around 68-72. How do you know the company plating it is doing a post treatment hardening? How does anyone know what they are buying or who made the parts? Look at some of the instructions and notices on the websites. Y/M (Young)says they don't stake the screws in the carrier keys...TDP calls for staked screws. YHM says hand tighten barrel nuts...! Everyone should know thats crazy.
The TDP says carpenter 158 for bolt material. Alexander Arms uses 9310 like many others. Some companies have been using 8620 to make bolts for years. You can't improve the strength of a material over the max yield spec given by the company that produces the steel by using a different heat treat. You can however make it weaker by using the wrong heat treat. The only way to improve the strength of a bolt is by adding material or using a different material.
We hear about bolts breaking fairly often. IMO the number 1 weak link of the entire system. Could be the reason they say bolts should be replaced around 5000 rounds. I only know of 1 barrel extension failure. It was a Olympic Arms/Dtec WSSM( a .555" diameter 65,000psi cartridge). Are barrel extensions high on the concern list...I don't think so but you seem to be hung up on hoop stress, the tenon and the extension.
Stainless barrels don't come anywhere near the strength of 4150 or required for the cartridges but I haven't heard of any barrels exploding.
The TDP calls for 4150 11595e steel, chrome lined. Do you want to shoot a chrome lined barrel in an F class match? What I know is we can make barrels from 4150 11595e and have the same strength as a TDP spec barrel.
By Meloniting the barrel we can improve the accuracy over a chrome lined barrel without losing the strength. The TDP is great for combat rifles but it doesn't always spell out the best specs for every purpose civilian rifle.

As far as I am concerned everyone should do their own research, dig up the facts yourself and don't believe the BS that you read on forums. Companies that have sold 10s of thousands of parts and have no record of broken bolts or extensions or exploding barrels are probably safe. Companies producing bad parts will self destruct.

BTW, Where's the photo of that barrel extension? I'm thinking it must have been machined wrong to have feed ramps that thin.

The extension on the left(silver) was placed in a round part vice we use to hold barrels while torquing the extensions. It shattered before I could get the vice as tight as I wanted it. Notice there is no deforming...it did not bend at all, just shattered. The extension on the right has been Melonite treated. It was placed in the vice before the other and tightened as much as I could then I struck it 8-10 times with a 20oz hammer at full swing before I could bend the end where the lugs are and crack the extension.
It's pretty easy to tell which extension is more brittle.
Attachment 29093

[LRRPF52]

The engineer came to my house. He's a personal friend/shooting buddy, no big deal really.

It seems like you're looking for an argument, or have some type of complex regarding this, when you weren't even mentioned in the discussion, which I find odd. It comes across as defensive, but for what reason?

The irony of it all is the source of the barrel in question. The threads on it are also such that torquing on a 1/2x28 muzzle device is horrendous.

[LRRPF52]

The takeaway for me as a consumer who actually shoots in high volume is that the barrel maker, barrel extension maker, salt bath nitriding shops, kilns, and raw steel suppliers form a production chain, with the guy putting all the components together being the last level of QC before it goes into a retailer's online store, or directly to the consumer.

What I'm seeing is that there are big question marks as to the competency of several layers of that production chain, and it often lies at the feet of the barrel assembler/finisher. The biggest factor in whether a shop is competent or not can be determined by their level of engineering expertise and how that pertains to firearms in particular.

For example: When I spoke with Burlington's engineer/process manager, he was highly competent about salt bath nitriding, but more importantly, he was intimately familiar with QPQ for AR15 barrels in lots of hundreds, with several different customers. I didn't ask any information about specific customers, as it's none of my business, and should be protected by NDA anyway. I just wanted to know if salt bath nitriding over case hardened 8620 extensions could result in the problem I encountered, which I've never seen on any other extension.

This isn't the first nitrided extension I've polished either, which is what made it stick out more to me. My questions were thoroughly answered though, and that was that nitriding can through-harden in acute angles, and that is exactly what we have on feed ramps-acute angles. Since the teeth in the extension are at right angles, I feel a little more comfortable about the extension's ability to bear shock force and stress under bolt lug loading, but I'm concerned that my BTHP ammunition will hang up on the chipped edge of the right feed ramp. I'll probably just shelve the barrel and consider it a lesson learned.

[constructor]

The takeaway for me as a consumer who actually shoots in high volume is that the barrel maker, barrel extension maker, salt bath nitriding shops, kilns, and raw steel suppliers form a production chain, with the guy putting all the components together being the last level of QC before it goes into a retailer's online store, or directly to the consumer.

What I'm seeing is that there are big question marks as to the competency of several layers of that production chain, and it often lies at the feet of the barrel assembler/finisher. The biggest factor in whether a shop is competent or not can be determined by their level of engineering expertise and how that pertains to firearms in particular.

For example: When I spoke with Burlington's engineer/process manager, he was highly competent about salt bath nitriding, but more importantly, he was intimately familiar with QPQ for AR15 barrels in lots of hundreds, with several different customers. I didn't ask any information about specific customers, as it's none of my business, and should be protected by NDA anyway. I just wanted to know if salt bath nitriding over case hardened 8620 extensions could result in the problem I encountered, which I've never seen on any other extension.

This isn't the first nitrided extension I've polished either, which is what made it stick out more to me. My questions were thoroughly answered though, and that was that nitriding can through-harden in acute angles, and that is exactly what we have on feed ramps-acute angles. Since the teeth in the extension are at right angles, I feel a little more comfortable about the extension's ability to bear shock force and stress under bolt lug loading, but I'm concerned that my BTHP ammunition will hang up on the chipped edge of the right feed ramp. I'll probably just shelve the barrel and consider it a lesson learned.

You're pretty good about posting photos and graphs and quoting articles. Just post a photo of that chipped extension in a receiver with M4 ramps. It seems to me that if the ramp of the extension is chipped it would form a condition where the bullet will hit the receiver ramp and then skip over the edge of the extension. The problems occur where the extension ramps overhang the receiver ramp which you obviously ground away.

ETA-I did comment on the TDP. For combat firearms it is a good thing but for civilian use I would rather have a Melonited 4150 barrel to gain accuracy over a chromelined 4150 barrel. I would rather use the stronger 4150 alloy instead stainless barrels. 4150 has more burst strength and last longer than stainless or 4140. The rest of the rifle could be TDP compliant.
S&W, Springfield, LWRC, Glock are using Melonite. We've sold tens of thousands of barrels since 2008 and haven't had any complaints except the barrels are so slick it's tough to get paint to stick to it. I haven't seen any bad reports about other manufacturers melonite treated barrels either.
Those that know enough to use good parts know where to find them. Those that don't know are still over on arfcom reading...all excited. Sooner or later some will learn, some wont. Think about it, some 40 year olds still think a long freebore is designed for long ogive high BC bullets and the neck of the cartridges center the bullet on the bore.
http://bulletin.accurateshooter.com/...s-and-actions/

[Iraqgunz]

Our Melonite barrels have been doing very well. However, we opted to not Melonite the barrel extensions for obvious reasons.

You're pretty good about posting photos and graphs and quoting articles. Just post a photo of that chipped extension in a receiver with M4 ramps. It seems to me that if the ramp of the extension is chipped it would form a condition where the bullet will hit the receiver ramp and then skip over the edge of the extension. The problems occur where the extension ramps overhang the receiver ramp which you obviously ground away.

ETA-I did comment on the TDP. For combat firearms it is a good thing but for civilian use I would rather have a Melonited 4150 barrel to gain accuracy over a chromelined 4150 barrel. I would rather use the stronger 4150 alloy instead stainless barrels. 4150 has more burst strength and last longer than stainless or 4140. The rest of the rifle could be TDP compliant.
S&W, Springfield, LWRC, Glock are using Melonite. We've sold tens of thousands of barrels since 2008 and haven't had any complaints except the barrels are so slick it's tough to get paint to stick to it. I haven't seen any bad reports about other manufacturers melonite treated barrels either.
Those that know enough to use good parts know where to find them. Those that don't know are still over on arfcom reading...all excited. Sooner or later some will learn, some wont. Think about it, some 40 year olds still think a long freebore is designed for long ogive high BC bullets and the neck of the cartridges center the bullet on the bore.
http://bulletin.accurateshooter.com/...s-and-actions/

[LRRPF52]

Here are some pics of the nitrided extension that chipped like glass with the mere touch of a rubber Cratex polishing bit. You can see it on the right feed lip. I've done scores of feed lip jobs where the lips don't match the extended M4 ramps, even with M4 extensions, because the industry is all over the map when it comes to matching these parts up. For those of us who shoot a lot of 68-77gr BTHP's, we like to have a smooth transition there, with no possibility of the meplat catching on the edge of the feed ramps of the extension.

There has been a learning curve for some manufacturers on QPQ/ferritic nitrocarburizing, which is why I think I got this barrel at such a low price. $170 for a fluted, CMV, .223 Wylde chamber seemed about 1/3 of what I should have been paying, but I rolled the dice. I had it in a rifle upper without ramps before, and was planning on moving it to an M4 upper. The index pin was also sharply cut of with grinder marks on it, with no consideration for clearing the female threads of a barrel nut, so I radiused it and made it so that it would perform as expected.

After having a mechanical engineer look at it, he said it appeared to be through hardened, and kept asking me if I had dropped it on a hard surface. There is also some galling on the bottom of the 3 o'clock tooth of the extension, which looks like it could have come from installation with the barrel extension tool. The barrel is quite accurate though.