S&W Melonite coated barrel vs Noveske chrome lined barrel.

[CC556]

Melonite cannot prevent throat erosion. Surface hardness of material does not affect a materials resistance to a pressurized jet of hot flame.

Nothing can prevent throat erosion. Take a look at the long range rifle world though; melonite is gaining popularity because it does help slow throat erosion, and it does it without changing the bore dimensions like chrome lining does.

[SomeOtherGuy]

Melonite cannot prevent throat erosion. Surface hardness of material does not affect a materials resistance to a pressurized jet of hot flame.

Taking the same view, the hardness of chrome doesn't prevent throat erosion either. Yes this is contrary to experience with throat erosion in chrome-plated bores.

I'm not an expert but I think throat erosion would have at least three components:
1-vaporization of material purely from heat
2-wear and scouring of material from solid particles (still-burning powder grains and primer residue) moving across it
3-oxidation or other corrosion from the hot gases

For #1, the two factors controlling would be the melting and vaporizing temperatures of the material and its heat capacity.

For #2, ordinary abrasion resistance (at the relevant temperatures) should control.

For #3, corrosion resistance should control. (I'm aware that most powders are either carbon-rich or otherwise formulated to limit oxidation and other chemical corrosion.)

Looking at these, we would see that ordinary 4140 or 4150 steel has a moderately high resistance to heat and abrasive wear, and little resistance to oxidation.

Chrome plating will be somewhat higher in melting point, significantly higher in abrasion resistance and dramatically higher in corrosion resistance.

Nitrocarburized layers on steel will be even higher in corrosion resistance, in the same ballpark for abrasion resistance, and I simply don't know what their melting points or heat capacity would be.

I'm interested to hear any further development on these factors affecting wear.

Edit to add: there could be a major difference in durability of a material depending whether it's used in slow firing, with the bore at close to ambient temperature before each shot, or rapid fire where the bore may be used largely at high temperatures (500-1000 F.). This is one reason why Stellite is so useful in machineguns, even though its ambient temperature properties are not all that special - as a cobalt alloy it holds its hardness and wear resistance at a higher temperature than most other metals suitable for use as a bore liner.

Put another way, it's possible that one material could have the longest bore life when used in slow fire, and a different material could have the longest bore life when used predominantly in rapid fire.

[MarkG]

50 years of empirical data on chrome lined barrels. Zero vetted data on nitrocarburized RIFLE barrels.

The firearms industry is filled with TRICKSTERS. I find it amazing that self reporting is not only tolerated but celebrated in this industry. S&W claims of barrel life are just that, claims. Independent verification is all that we should be discussing but it doesn't exist.

[SomeOtherGuy]

50 years of empirical data on chrome lined barrels. Zero vetted data on nitrocarburized RIFLE barrels.

Two US Army test reports are linked in my post #20 in this thread. I would consider them reliable data for the metallurgy and surface treatments existing at 1969. They clearly indicate that nitrocarburizing is dramatically more wear resistant than plain steel, but at that time inferior to chrome lining. There is not a complete absence of data.

I would agree that I have not seen more recent independent comparisons of these two common bore finishes. Either or both of them could have improved since 1969.

[kartoffel]

For those who haven't seen it before, there's an actual US Army study of barrel wear with different finishes. Download it here:

http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf

In short, they concluded that nitrocarburizing significantly increased barrel life vs. plain steel, but chrome plating increased barrel life to an even greater extent.

Another study on machinegun barrels can be found at:

http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf

That study didn't look at ordinary chrome plating. It determined that Stellite liners were by far the best, with nitrocarburizing far ahead of plain steel.

This! Thank you for linking some good, solid references.

Melonite is no slouch, but for throat erosion in rifle barrels, hard chrome is demonstrably better. S&W most likely uses Melonite because they're already set up for Meloniting huge batches of handgun parts. It's not an awful choice.

* If I were building a 5.45x39 upper, I'd pick Melonite over chrome lined specifically for the corrosion resistance.
* For a general purpose gun: hard chrome, hands down.
* For precision: bare naked stainless steel.

[GrumpyM4]

Grumpy,

I'm not one of Sotts fans, not because of what he says generally, but because of the delivery. With that out I think in this case what he says makes perfect sense. To me it's unrealistic for one member to demand "proof" on questions such as these. Unless we work in a field that directly applies to metallurgy and coatings and such we will not have it.

I do not believe that it's unrealistic. I've already seen much of the data and researched the effects of various types of nitrocarburization processes and Chrome lining.

Simply typing "Chrome vs. nitrocarburization" brings up lots of data. A simple search for types of nitrocarburization processes is eye opening in and of itself.

This is not a personal attack on you at all. I find it ironic that people consistently scream at one another for facts when they have the same capability as most members of taking the time to look for and post them.

Didn't take it as a personal attack. I may disagree, but at least your delivery was much better.

[GrumpyM4]

Do you really believe a glock slide can withstand a blow torch because it has a melonite/tenifer treatment? I noticed how you couldn't answer and didn't addres this point in your poor rebuttal.

And do you believe that chrome lining magically makes steel impervious to your blow torch?

Prove it already.

And, as it were, I had no rebuttal. All I did was ask you to BACK UP what you're saying. I have nothing to answer for because I havn't made any claims one way or the other, especially with no facts to back them up. That appears to be your forte.

I'd love to have some real test data from both sides of the camp. You're clearly in the chrome camp, so, by all means, back up your statements.

[GrumpyM4]

Melonite cannot prevent throat erosion. Surface hardness of material does not affect a materials resistance to a pressurized jet of hot flame.

So all nitrocarburization amounts to is "surface hardening"?

You mean to say that it's not also an anti-corrosion treatment?

One can merely harden almost any kind of metal, but that does not magically grant it corrosion resistance. Whereas the ferric nitrocarburizing process hardens AND infuses nitrogen and carbon into the steel thereby imparting respectable anti-corrosion capabilities.

To what extent is this effects throat errosion in a firearm is yet to be proven as even I can see that S&W's claim of "no visible" damage is highly subjective. (and for what it's worth, I do believe that their high round count was across 5 or so different test guns if I remember correctly, rather then in a single rifle)

That being said, what does chrome do? It is a harder metal bonded to the outer surface of a steel that imparts some corrosion resistance. Some say less corrosion resistance then melonite (http://www.finishing.com/497/37.shtml ), and acts as a "hardened metal" buffer between the rounds being fired and the base metal of the barrel. Does not Ferric Nitrocarburizing do virtually the same thing? Only it does it by changing the properties of the outer layer of the base metal rather then adding a seperate layer of a different kind of metal.

This site: (http://www.hefusa.net/melonite-QPQ-arcor.htm) even claims that "Wear and corrosion properties are superior to hard chrome
or nickel plating for many applications." Not saying that one of those applications is gun barrels, but it just may be.

Heck, even an old thead here on M4carbine seems to be heading in the opposite direction from what you say. Still inconclusive, but heading in that direction. (https://www.m4carbine.net/showthread.php?t=38124&page=2)

Funny how you hopped in that thread in nearly the exact same manner that you did here with nary a fact to back up your statements.


Some more nitriding references:

http://www.riflebarrels.com/articles/barrel_life1.pdf

http://www.finishing.com/324/69.shtml (of particular note are the enteries starting Oct. 17 2010 and after)

[NorthDakota]

Is this a real question?

Yes.

[scottryan]

And do you believe that chrome lining magically makes steel impervious to your blow torch?

I never said it did.