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本帖最后由 StarFox000 于 2022-7-31 07:40 编辑
Chrome Moly Vanadium Steel
CM and CMV (Chrome Moly Vanadium) is the term Colt used for their AR barrels. CMV is basically 4150 steel with the addition of vanadium.
If you look up the mil-spec documents for CMV barrels (specifically MIL-B-11595E), the composition is literally the same as 4150 steel with some vanadium added.
Now, why that’s important has to do with the nature of vanadium.
Vanadium, a transition metal, gives alloys higher tensile strength but also has the advantage of forming an oxide layer on the surface of the material.
In plainer English, it makes things stronger (actually harder, but never mind) and more resistant to rust than regular steel, which requires a coating or regular treatment of a preservative.
Plenty good for any application, and it should last if you take care of it.
410 Stainless
The 400 series are steels with a high chromium content, often around 11 percent. The addition of chromium and sulfur is the definitive characteristic of these stainless steels, as it’s part of what creates the gray appearance.
This series includes the 440 stainless steels, commonly used in knives.
410 Stainless steel (as defined by the SAE) has a high chromium content and a higher sulfur content (with added molybdenum) than standard steel, creating a harder alloy than 4000 series…but also one that’s more brittle at cold temperatures.
Unless the chamber and bore are lined or otherwise treated, it is also more prone to corrosion than carbon steels. However, it is also harder to work with than carbon steel, so 410 stainless barrels tend to be a bit more expensive and made more for precision shooting applications.
416 and 416R Stainless Steel
416 stainless steel is an SAE formula, but 416R is a proprietary modulation of that formula made by Crucible Industries. 416 has a higher sulfur content than 410 and is easier to work and machine, but is also more brittle and wears very quickly.
Ever notice bargain-basement uppers that have a stainless barrel? Chances are they’re made of 416, and the rifling will wear out in a few thousand rounds.
416R, however, reduces sulfur content and adds more molybdenum. 416R is harder than 410 and can be safely operated at cold temperatures. While it has the hardness, strength, and the same capacity for uber-consistent rifling as 410, it’s easier to work with.
The combination of ease of work, along with enhanced resistance to corrosion and wear, make 416R a very popular material for AR barrels…but also more expensive.
Start naming an aftermarket producer or match-grade or otherwise high-quality pistol barrels, and they use 416R. Wilson Combat, Apex Tactical, you name ’em, and that’s what they use.
Should I Get Nitride Vs. Chrome-Lined?
Another aspect you might consider in an AR build is the coating and barrel lining, specifically a nitrided barrel vs. chrome-lined?
What’s the difference?
A chrome-lined barrel is electro- or chemically plated, similar to other industrial processes. Typically the bore has to be etched or otherwise scored for uniform adherence to the surface. Once applied, chrome is highly resistant to corrosion, heat and very resistant to wear.
Nitriding diffuses nitrogen into the surface of the metal. Typically, it’s done by a cyanide salt bath; the barrel and the salt are heated until the correct temperature is reached, and into the salt, the barrel goes. After a few hours, the metal has absorbed the nitrogen, and it’s done.
The nitrogen diffuses into the surface of the barrel metal, forming a crystalline structure on the material’s surface. Nitriding makes the material harder and far less susceptible to oxidation.
What’s the difference?
Chrome-lining is more expensive and requires the barrel to be roughed before lining, which can theoretically reduce mechanical accuracy…but the degree to which it happens is typically small.
A sub-MOA barrel will not become a 3 MOA barrel with chrome lining, but a 1 MOA barrel might become a 1.2 MOA barrel.
Nitriding is cheaper but still incredibly resilient. Most factory barrels of any sort are nitrided, either as the finish or part of a finishing process. Name a popular gunmaker – whether of rifles or pistols – and some or all of their products have a nitrided barrel.
Nitriding is less wear-resistant than chrome lining, but the question is whether it’s to the degree that actually matters in the real world.
For most civilian purposes, it doesn’t. Very few people will ever subject their barrel to enough heat or other stress to even come close to ablating a nitride finish from the barrel.
Chrome lining is essential in certain instances, for instance, if you’re exclusively shooting steel-case ammunition with corrosive primers (only capitalists don’t maintain rifle, comrade) or for a machine gun. And arguably less so in the former case if you actually take care of your guns
Unlined barrels, which are only common with bargain-basement stainless steel barrels, as mentioned previously, should be avoided unless you intend on replacing them as they will quickly wear out.
So, as far as finish goes, nitride is perfectly sufficient unless you’re getting an actual machine gun that you’re going to fire a lot on full-auto. While price tags would suggest lower quality, that isn’t the case…but cheaper steel is still cheaper steel. So invest in good steel first.
https://www.usacarry.com/ar-barrel-steels/ |
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发表于 2022-7-30 22:17
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