My understanding is that, for hard use barrels, chrome lining is superior to Melonite. For the average weekend target plinker there’s not much difference. Sound about right?
Yes. But Melonite barrels can take a pretty good beating too.
So for a full auto rifle stay away from melonited barrels? I shot full auto with a Sig 516 10.5 barrel. Should I stay away from going full auto with it? It’s nitride
I wouldn’t use a nitride barrel as an LMG, but it will probably do fine at moderate full auto. Since most us are running semi anyway, getting to temps that high takes a lot of effort.
Chrome is still king because it’s a known quantity. It is still very good at what it does, and is probably the safer choice for something you intend to abuse.
I wouldn’t treat it any different. I don’t know how hard a 516 barrel is to get/replace. There are guys her who have a better knowledge of the QPQ durability than I though… we haven’t shot any barrels out yet, so hopefully someone with a higher round count example will post.
If I had my druthers I’d take chrome lined over nitride/Melonite/QPQ.
As stated above, chrome lining is a known quantity.
Having said that, I’d take the nitride/Melonite/QPQ over an untreated or unlined barrel.
If by hard use you mean mag dumps after mag dumps (or belts) of automatic fire, then yes, hard chrome will handle the extreme heat better. Otherwise melonite/QPQ/nitride is superior in every way.
The InRange guys did a very thorough video series about barrels, which covers this in much with much depth and knowledge. Everything you ever wanted to know about barrels essentially. There’s 4 videos.
I remember watching that a while back. As far as Melonite et al. being “superior in every way” to chrome save for use in guns that are fired extensively on full auto, I believe one of Faxon’s qualifiers for that was “as long as it it’s done right” and that not everyone who does meloniting does it right.
It seems kind of like how I’ve heard that 9310 steel is actually theoretically superior to Carpenter 158 for bolts “As long as it’s done right” during the manufacturing process, and that at this stage in the game not everyone who does it does it right, therefore C158 is still the safer bet for bolt material.
Chrome needs to be done right too.
The difference is chrome is far harder to do properly than Melonite.
And more costly too! That is, I believe, the driving force behind the increased trend towards Melonite et al.
Quality of the barrel is important. A quality Melonite > shitty Cr lined.
Quality Cl>shitty melonite.
All else equal, there may be trends one way or another, but base quality is key
Yes.
It seems there are a million ways to screw up a barrel.
Each step must be done properly to ensure a good result.
Smith & Wesson seems to be a major user of Melonite on their rifles and handguns. They call it “Armornite” or some such.
I’m not seeing this as a binary solution where one is better than the other.
I am probably wrong, but wouldn’t QPQ barrels wear a little more like SS barrels? Once the hot gasses erode the QPQ permeated steel, throat and gas port wear would be rapid? Where as CL is more of a slow degradation of accuracy due to it acting as a heat shield?
(All things given equal on the barrel).
So if we assume that nitride is the most appropriate treatment/lining for a barrel, where can I find a list of makers that are GTG, or a list of do-not-buy barrels? I’ve avoided them up to this point because of barrel extension horror stories, and because chrome is a relatively known quantity.
You know what happens when we ass-u-me, right? 
Ft. Benning comes to mind when that word slipped out of a fellow recruit’s mouth.
Don’t assume that nitride is superior. To me, and a lot of others, it isn’t. It is a less expensive (read: cheaper) shortcut to protecting a barrel. The ONLY advantage I’d give it is that both the inside and outside of the barrel is treated, whereas with chrome lining only the chamber and bore are. Even given that I’d still take a quality CL job over a quality nitride job in a heartbeat.
Melonite is provably superior to chrome in dimensional consistency.
Melonite is a treatment that does not change the bore diameter or the shape of the rifling at all.
If the rifling was good and the process is done properly, the rifling will be the exact same shape, but harder and stronger after the treatment.
In contrast, chrome is an electro deposited coating that builds up thickness and does change the shape of the rifling.
The “how much” it changes the shape and how much it matters is a separate topic.
The Chrome layer deposit is often proceeded by an electro polish step that is the theoretical inverse of coating.
Both process selectively affect sharp edges and corners more than other areas.
The polish enlarges the bore diameter to compensate for the thickness of the chrome, but it rounds off corners (edges of lands and grooves) too.
The chrome reduces the bore diameter back to spec and sharpens the corners, hopefully back to where they started or at least to a shape that works well.
http://www.uschrome.com/design-recommendations-for-hard-chrome-plating
So, a barrel intended to be chrome line must be over bored slightly before plating to account for the thickness of the chrome?
Yes, either with a chrome specific “button” or with an electro polish process.
Evidently, this process has been around for a while, as this old report from 1937 indicates:
http://www.dtic.mil/dtic/tr/fulltext/u2/701179.pdf
I was not aware until I did some research that the Japanese were the first to chrome-plate small arms barrels (their Type 99 rifle). In part, chrome-plating meant that they could use lower-grade steels than would normally be accepted for rifle production.