Stainless Steel Barrels: 410 vs 416 vs 416R

[MistWolf]

Then you should have gotten the James Stewart reference

Yes. Or at least I would have if I'd remembered seeing the movie...

[InoxShooter]

"416R is a proprietary steel produced by Crucible specifically designed for rifle barrels." This is true but most stainless steel manufacturers make a "firearms" quality 416 grade of steel. The largest stainless steel manufacturer in the world makes 416RQ and 416FQ (http://www.outokumpu.com/SiteCollect...s/Firearms.pdf)

I just wanted to let everyone know that most stainless steel manufacturers don't sell generic 416 for use in firearms. So if a barrel is being sold as 416 it is most likely not the generic 416 but a firearms quality 416. Saying the a barrel is "Made from Crucible 416R Stainless Steel" is more for marketing then really distinguishing the quality of the 416 grade steel in the barrel.

[mpom]

Surprised no one has stirred the pot by bringing in Nitrided/Melonited SS till now. Not sure if anyone has done destructive or long term testing to see how it compares to chrome moly, 410 or 416R, but from reading related threads on M4C, it seems that wear and corrosion resistance are enhances over untreated state. Brownells sells a line of barrels under their label made of Nitrided 416R. http://www.brownells.com/rifle-parts...prod56797.aspx
Where does this version of SS fit in with respect to the steels discussed in this thread?

Mark

[Badger89]

"416R is a proprietary steel produced by Crucible specifically designed for rifle barrels." This is true but most stainless steel manufacturers make a "firearms" quality 416 grade of steel. The largest stainless steel manufacturer in the world makes 416RQ and 416FQ (http://www.outokumpu.com/SiteCollect...s/Firearms.pdf)

I just wanted to let everyone know that most stainless steel manufacturers don't sell generic 416 for use in firearms. So if a barrel is being sold as 416 it is most likely not the generic 416 but a firearms quality 416. Saying the a barrel is "Made from Crucible 416R Stainless Steel" is more for marketing then really distinguishing the quality of the 416 grade steel in the barrel.

I would like to see the composition chart for the 416RQ and 416FQ you mentioned.

Advertising rifle barrels as 416R may be a marketing technique, but you cannot discount the fact that there is a very real difference in the composition of 416R compared to standard 416. Therefore, it's not just a fancy name, it's actually a different steel.

[Badger89]

Surprised no one has stirred the pot by bringing in Nitrided/Melonited SS till now. Not sure if anyone has done destructive or long term testing to see how it compares to chrome moly, 410 or 416R, but from reading related threads on M4C, it seems that wear and corrosion resistance are enhances over untreated state. Brownells sells a line of barrels under their label made of Nitrided 416R. http://www.brownells.com/rifle-parts...prod56797.aspx
Where does this version of SS fit in with respect to the steels discussed in this thread?

Mark

There are two main reasons I did not bring up melonite treatment. First, because it is only a surface treatment, not a separate "version" of stainless steel, and does nothing to alleviate the problems of temper embrittlement and sulphide stringers in the host material. Second, because there is no good way to melonite an AR/M4/M16 barrel. The best way to do so is before the gas port is drilled and the barrel extension installed, which leaves you with an untreated gas port after drilling. The more common way (an less desirable) is to treat the entire barrel assembly (sans gas block) after the gas port has been drilled an the barrel extension attached. This is less desirable because the salts used in the process will get in between the threads of the barrel extension and the barrel and can cause corrosion over time. Removing the barrel extension to clean the threads after treatment means that you will likely not be able to re-torque the extension to the proper spec AND get the gas port to line up at exactly 12 o'clock. If someone has figured out a way around this, I'm all ears.

That said, melonite treatment is a viable process for case hardening carbon steels and 17-7PH stainless steel and improving corrosion resistance of the same. Glock slides and barrels, AAC flash hiders and muzzle brakes, and various gas blocks come to mind. Martensitic stainless steels can also be case hardened through meloniting, but they do not gain much in terms of corrosion resistance. They also must be exposed to 900 - 1,000 degrees Fahrenheit (roughly 480 - 540 degrees Celsius) for a period of 30 to 120 minutes to complete the process. Tempering of martensitic stainless steels within this temperature range greatly reduces their impact resistance. Put another way, you may be doing more harm than good.

There are quite a few threads already discussing the topic of melonite treatments and how they relate to barrel performance. I'd prefer to avoid the inevitable johnson measuring contest that seems to always accompany that topic and focus on discussing the differences between stainless steels and their suitability for barrel making.