When did I ever say or imply this?
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The study unfortunately invalidates its own usefulness in comparisons by using a plain, unplated barrel as the control instead of a standard chrome-lined barrel, but it's a worthwhile read nonetheless.Quote:
Abstract: The procedure as developed by Springfield Armory for design and fabrication of a stellite-lined, chromium-plated barrel for the 5.56mm machine gun is described. Results of erosion tests of the stellite-lined barrels, standard barrels, and two other types of barrels show that the stellite-lined barrels are superior in erosion resistance. One of the stellite-lined barrels was fired 43,994 rounds prior to rejection. A maximum of 12,476 rounds was fired from one of the standard barrels prior to rejection. The two other types of barrels - a standard barrel with a nitrided bore and a barrel of two-piece construction - were fired 29,874 and 990 rounds, respectively, before rejection. The two-piece barrel has an 18-inch forward section made from Cr-Mo-V steel and the rear section, including the chamber, is made entirely of stellite. All barrels were rejected on the basis of the projectile instability criterion - 15 degrees of yaw of 20 per cent of the projectiles fired. All barrels were fired at an average rate of 200 shots per minute.
-B
Making no mention of the other properties of nitrogen and carbon enhanced steel.
Implication? Maybe, maybe not. Glaring omision? Yup.
Don't ask me, ask S&W. I don't work for them so I have no idea how many rounds per firearm, although I was wrong about the number of guns S&W claimed to have used.
According to this: http://thetruthaboutguns.com/2011/06...on-mp15-sport/, it was only two rifles.
So, all that aside, come up with any facts yet?
some great info here, i was wondering about what the general thought was on the MP sport Melonite barrel. I love the finish on my MP's, but knew nothing of how it would perform as the lining of a AR barrel.
And you could just as easily come up with an even longer list of hobby-grade rifles that have chrome lined barrels. It doesn't prove anything. Do you have any hard data at all, or are you just hoping you can toss out some disingenuous and simplistic responses to distract people?
Scottyryan: Hey, I have no dog in this fight, but I do have a question for you. Do you think that a salt-bath nitrided will be any less robust/durable than a CL barrel?
FWIW, in addition to my CL BCM middy, I just had an upper put together using a Rock Creek barrel that uses 4150 CMV steel with 5R rifling. The barrel was nitrided by Rock Creek in a salt bath, which is supposed to be the most effective means of nitriding a barrel. As long as it's not any worse than CL, I'll be happy, as initial range groups appear to show that it's probably gonna be a 1 to 1.20 MOA rifle with 75gr TAP.
Thanks.
Not that I know of for #1.
For #2, the US Army has done so, see the first study linked in my post #20 (which is a small arms barrel study and different from the machinegun study that was posted by both me and another). That is of course 1969 level technology and results might have changed since then.
The fact that those barrels had a Stelite insert in the throat area makes it an invalid comparison.
Stelite is some serious shit. We used to dog the living crap out of M-60's with leftover ammo and the barrels took it and asked for more. The barrel was the best feature on the Pig.
Ma Deuce also uses them too.
Situational awareness fail for me for reposting the same study you did. :o
Having said that, as I stated the study invalidates itself as a comparative tool since it does not test a standard chrome-lined barrel against an otherwise-equivalent nitrided barrel. Facts have been pretty well nonexistent where the benefits of chrome-lining vs nitriding are concerned. A lot of hearsay, but no numbers to prove or disprove. Scott definitely has a point in the expense involved in such testing, but without somebody shelling out that cash we'll never know definitively.
Take ten equivalent barrels, five chrome-lined and five nitrided, and shoot them to destruction. It's really the only way to settle this.
-B
Cost is no proof of effectiveness
I have no specific studies or scientific data to offer up, but I can tell you that the salt bath ferritic nitrocarburization process is becoming more popular in the benchrest game. Many of the hot running 6mm cartridges popular in that sport induce throat erosion and general wear and tear on the barrel in a suprisingly small round counts. Unfortunately I can't find the thread, but there was a discussion on the Hide about this. One member who shot 6mm benchrest did a comparison between an untreated barrel and one that had been nitrocarburized. He measured throat erosion and kept a round count for both. Since I can't find the post I don't have numbers but the gist was that the treated barrel was resisting wear markedly better than the untreated (it was also equally accurate). Now, granted, the control barrel was not chrome lined for obvious reasons so the comparison is not 100% relevant for AR type rifles. But, I think one thing we can take out of this is to find a middle ground. I think we can agree that in SOME applications, the nitriding process is a good choice. Perhaps in a precision rifle where chrome lining would be a detriment to accuracy and the user didn't want stainless. I guess what I'm getting at is you can't simply call the process junk, or assume that it's just a cheap alternative to something better. The accuracy freaks in the benchrest game obviously believe there is merit to the process. Only time will tell if it's a legitimate alternative to chrome lining. As to why you're only seeing it appear on rifles on the lower end of the spectrum, think about it this way...the users that purchase expensive top of the line AR's are generally pretty knowledgeable, and what comes with that is that they're set in their ways. They're not going to shell out the big bucks for something they see as "experimental" when they just "know" that CL'ing is the way to go because that's what they're used to and that's what's MILSPEC. I simply don't think it would sell well. Maybe the uninformed purchasers of low end AR's that you're seeing these nitrided barrels on are being used as beta testers for the process by the manufacturers. They'll never come out and say that but it's not an unreasonable notion. Time will tell I suppose.
1. It's not a blow torch.
2. A cutting torch provides sustained heat from a 6,500* flame whereas a round going off in the chamber is only a split second.
3. Cutting torches don't use heat to melt or cut steel. They use heat to induce a super intensified rusting of the metal from pure oxygen.
4. The steel is able to be cut with the oxygen jet before it becomes molten.
What does all this mean? That heat is only one of many factors in throat erosion. After being a boilermaker I've learned a few things about the performance of various metals at elevated temps for prolonged periods of time and I'll tell you right now that hardness is ABSOLUTELY a major player in the matter.
Metal gets soft at elevated temps. Soft metal wears easily. Carbon is very abrasive. Hot gases are very abrasive. Burning gun powder is full of both. Therefore the whole game is about finding a metal that stays hard and resist corrosion at high temps. Nitriding does both exceptionally well and that's proven fact. So what are you arguing? That it doesn't or that it's not as good as chrome? If the former then the facts say you're wrong. If the latter then show us what you base you're argument on.
To be honest most of the steels used for barrels aren't even the best choices. Theirs some pretty amazing alloys out there that would blow people away that are in regular use for boiler systems as well as other high temp applications (and I've cut most of them with a torch).