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To Chrome or not to Chrome? Myths and Facts of Chrome-Lined Barrels

Ever since the military began chrome-lining barrels on standard issue machine guns and rifles there has been debate concerning the benefits and disadvantages of chrome-lined barrels. Many of the benefits of chrome-lining are shrouded in myths and misconceptions. Chrome-lining protects the barrel from corrosion, but this is not the main purpose for lining a barrel. Chrome-lined barrels are also easier to clean, but the military would not invest in a chrome-lined barrel just to save a grunt some time swabbing out the bore.

Years ago, with the introduction of high powered machine guns and semiautomatic rifles capable of sustained high rates of fire, military armorers began to notice significantly increased barrel wear and erosion. Older models of the most powerful machine guns were capable of “shooting out” a barrel in less than 1,000 rounds! Chrome-lining was introduced to increase the barrel life, allowing more rounds to be sent down range in less time without the need to replace the rifle barrel.

Muzzle flash from an AR-15 rifle, demonstrating the immensely hot gases generated by powder combustion. Photo courtesy of bdjsb7 licensed under Creative Commons.

Nowadays, almost all military rifles are universally chrome-lined to protect the rifle barrel from excess erosion. AR-15 rifles are particularly prone to erosion when fired rapidly, in part due to the high velocity of the round, and in part due to the high pressures generated by the cartridge. While it’s not uncommon for military rifles to experience high rates of sustained fire, it’s also not difficult to fire a semiautomatic AR-15 at rates exceeding 100 RPM. Under sustained fully automatic gunfire, or rapid semiautomatic fire, an enormous amount of heat is generated. That heat is what can quickly ruin a barrel.

The leade (the unrifled portion of the barrel just forward of the chamber), as well as the first few inches of rifling, is subject to temperatures hotter than the surface of the sun and pressures exceeding 50,000 PSI. Under slow fire conditions this area is able to cool a sufficient amount in between strings of fire. Under sustained rapid fire however, there is no time for the heat to dissipate and temperatures soar into the thousands of degrees Fahrenheit. This can quickly cause damage by eating away at the rifling, “burning up the barrel” with the combination of extremely high heat and pressure. Hard chrome-lining the bore protects the leade and rifling with a thin coat of heat and pressure resistant chrome. This greatly extends barrel life in rifles that are fired for prolonged periods in full-auto or rapid fire semiautomatic modes by preventing damage to the leade and rifling.

There are many people who argue that chrome lined barrels are less accurate than an otherwise identical steel barrel. All things being equal, this is true, but for most shooters, the degree to which accuracy is lost by using a chrome-lined barrel is generally unnoticeable. A chrome-lining does diminish the sharpness of the rifling, but the accuracy loss from this is not insurmountable. Consider the Fabrique Nationale SPR rifle (what is essentially a gussied-up chrome lined Winchester Model 70) is capable of shooting a 1/2 MOA group at ranges up to 800 yards away. A sub MOA gun is a fine rifle by nearly anyone’s standards, and most well built chrome-lined AR rifles are capable of 1/2 MOA groups as well.

So, when should you go chrome lined? Most casual shooters will get by just fine with either chrome-lined or non chrome-lined barrels. The fact is, most of us don’t get out to the range often enough, nor engage in rapid fire when we do (most ranges prohibit the practice). Even shooters who occasionally engage in periodic rapid-fire with their AR-15 style rifle may not notice the effects of excess barrel wear for a number of years. A good non chrome-lined barrel can last for over 5,000 rounds before it begins to show a loss of accuracy. If you shoot 1,000 rounds a year, even blasting through a full magazine as fast as you can pull the trigger on ever range trip, it could take 5 years or more before any significant loss of accuracy begins to become apparent.

When deciding whether to get a chrome-lined barrel your budget may be the deciding factor. Non chrome-lined barrels are significantly less expensive than a similar chrome-lined barrel. For a shooter who wants to build a quality AR-15 with less initial investment, non chrome-lined barrels represent a great cost-saving measure, combining the inherent accuracy of a stainless steel or chrome-moly steel barrel with an acceptable barrel life for a hunting or sporting arm. The up front savings can easily outweigh the cost of rebarreling your AR years in the future.

For the serious shooter who needs maximum barrel life as well as accuracy, a chrome-lined barrel represents the best of both worlds. The accuracy lost from a chrome lining amounts to less than 1/4″ at 100 yards, a negligible amount for most AR rifles used in tactical applications. If you do decide to go with a barrel that is not chrome-lined, be aware that you can significantly reduce the barrel life by quickly dumping 3 or 4 magazines through it without stopping to let it cool down.

If you’re building a match rifle that will be used solely for competitions where you’ll be firing slowly and you need a great deal of precision, stick with a chrome-moly or stainless steel match grade non chrome-lined barrel. If you think you’ll ever want to use your AR-15 for tactical applications, or even just rapid-fire plinking, drop the extra cash and get a chrome-lined barrel. Otherwise, be aware that without a chrome-lined barrel your AR-15 should be allowed to cool between magazines in order to avoid damaging the barrel.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (33)

  1. Seems to be a problem for a newbie to join in discussions. Is it my email address? Is it COVID-19???
    Multiple attempts to join forum; leave comment; then WAIT for email that never comes. Would appreciate feedback.

    1. You’re free to join the conversion! Just note that all comments are moderated, so there might be a delay in your posting. Thanks for visiting.

      – Editor

  2. you have an error in your information, (is subject to temperatures hotter than the surface of the sun) that is incorrect. The sun surface is around 10,000 Fahrenheit. Sounded good but NO. The barrel can reach temps at 5,000 Degrees Fahrenheit.

    Who ever said that was thinking 5,000 degrees Celsius.

  3. Great article however I took issue with the claim that the barrel is subjected to a temperature hotter than the surface of the sun. The temperature of the surface of the sun is 5,778 K (5,505 °C, 9,941 °F).

    1. There is a process being tested by the US military that extends the life of a battle rifle 7 fold. Hexovalent chrome will soon be something of the past.

  4. Nitriding, such as Glock’s “Tennifer” process, and “Melonite”, creates a harder, more corrosion-resistant barrel than chrome. It’s more expensive, though.

    Chrome is a cheap way to gain a little marketing edge. Many high-end custom barrel makers won’t use chrome. They say it affects accuracy. They say, “clean your gun and oil it properly.”

    Chrome is more resistant to corrosion than bare steel, but anyone who has ever had a motorcycle…..or a BUMPER……knows that chrome is porous and WILL rust.

    Unless you have a machine gun, in which case you’re going to wear out the barrel pretty quickly anyway, the “hardening” effect of chrome lining is meaningless. A good barrel, properly broken in and maintained, will work great for tens of thousands of rounds. It won’t get anywhere near as hot as a machine gun barrel. Chrome is unnecessary, at best.

    1. And if you are using a Shilen or Dan Lilja heavy match barrel your single-shot bolt-action benchrest competition rifle, then perhaps you are one of the people who has reason not to use chrome.

      For the rest of us, well, it’s milspec for a reason. In the AR platform specifically, the low mass of the bolt carrier group means that when the gun is dirty it sometimes needs a bit of help with extraction. The original M16s had non-chrome-lined barrels, and extraction problems killed so many American soldiers that the M16A1 had a chrome-lined barrel to fix that problem. Even for non-AR platform rifles, chrome lined barrels are vastly easier to clean because they collect so much less fouling. Advantages: it reduces wear, it is faster and easier to clean, it helps extraction (especially with lacquered steel case ammo), it protects against corrosive primer residue (and recall how much corrosive-primed surplus ammo in various calibers is floating around out there). Disadvantages: approximately zero. But it costs money, so bargain-basement, fly-by-night AR parts vendors will sell barrels labeled as “chrome moly” instead of “unlined carbon steel” in an attempt at deliberate confusion, and write ad copy in which they claim their failed-QC, production-line-reject unlined barrels are somehow more accurate than a proper milspec barrel.

      Also, thin, porous, polished bumper chrome != the heavy industrial hard chrome lining that’s spec’d for barrels.

      Yes, a good barrel, well maintained, will work for many thousands of rounds. For those of us who contemplate the possibility we may have to “perform maintenance” by cleaning the rifle with diesel fuel and lubricating it with dirty used motor oil while sleeping in ditches or abandoned buildings for a few years, that doesn’t exactly inspire confidence.

    2. I donÔÇÖt own either,looking to buy 1st time,but the general idea to me from the(chrome lined barrel supporters is)No offense,if youÔÇÖre a LAZY ASS,and donÔÇÖt maintain your firearm properly,make damn sure you get a chrome lined barrel,almost all modern A R-15,with M-4 feed ramps,donÔÇÖt have the feeding problem.I just canÔÇÖt justify the price difference,at least at the two,major models IÔÇÖm looking at. Very comparable in parts quality.But 150.00 difference in price.

    1. My understanding is that Stoner did specify chrome lined chamber & bores.
      This was a lesson learned from earlier service rifles. The Army initially thrifted it out. The resulting corrosion from the extreme environmental conditions in Vietnam led to corrosion and pitting in the chamber. This resulted in case weld and failure to eject. The most prevalent and deadly failure until the chrome lining was implemented.

  5. In regards to the temp of the sun comments….I wouldn’t doubt that the author is accurate…the temp is only for a fraction of a second. Shoot, lightning is 30,000 to 50,000F for a fraction of a second too

  6. PLEASE: With all due respect, the author of the article stated that ‘The leade (the unrifled portion of the barrel just forward of the chamber), as well as the first few inches of rifling, is subject to temperatures hotter than the surface of the sun and pressures exceeding 50,000 PSI.’ Come on- The temperature of the surface of the sun is estimated at 10,000 degrees F!!!!! Would melt anything we know on earth. NOW, I question his/her review/article!! Jon

  7. In other words chrome-moly is crap. Read the last sentences of the article: “If you think you’ll ever want to use your AR-15 for tactical applications, or even just rapid-fire plinking, drop the extra cash and get a chrome-lined barrel. Otherwise, be aware that without a chrome-lined barrel your AR-15 should be allowed to cool between magazines in order to avoid damaging the barrel.” So that’s that for everyone I know; we want a real rifle to defend our families with if necessary. Sorry but bad guys won’t let us cool the barrels between magazines. Shame on anyone for selling this junk. Be advised, too, that the Rock River Arms new “LEF-T” left-hander ARs only have chrome-moly barrels available. These are sounding like a novelty gun – not serious for defense and not fully supported by the manufacturer. An email from them said that the left-hand twist in the barrel prohibits the chroming process, but a RRA moderator on a ‘board told me it was because of production limitations. See? The lefty gun is already in the back seat. Do I want to blow money on a chrome moly barrel and probably very hard to get spare parts? No.

  8. With my 308 and 6BR F Class rifles I use match grade stainless steel barrels for 600 yards. With 2900 to 2950 fps on the to, barrel life and grouping with show changes in the 1200 to 1400 rds range. While my 30BR used for the 100 to 300 yards and 2700 fps the barrels are still good at 3000 rds. My question lies in the use of a match grade stainless steel barrel vs. the chrome line steel barrel. I would think the chrome lined would have a much better life span. Changing barrels for a new one results in the re-zeroing the rifle and which loads will give the best groups. But that is with my loads and I do not intend to hand load 5.56, I will stick with the factory loads from Lake city.

  9. OP’s quote: “The leade (the unrifled portion of the barrel just forward of the chamber), as well as the first few inches of rifling, is subject to temperatures hotter than the surface of the sun”

    LMFAO… The surface of the sun is 9,940° degrees F, 5,778 Kelvin, or 5,500° C. That is about 4 times hotter than what it takes to melt steel. No part on the gun ever, EVER gets that hot. The gun would turn into liquid well before it hit the temperature of the surface of the sun.

  10. Great article. Also just wanted to say that chrome lined barrels are not that expensive. Examples, you can get a chrome lined WASR AK for $400. RRA has chrome lined barrels that are only about $45 more than their others, that’s less than a box of .44 mag ammo. Also I like the string about the Mini-14. The most underrated rifle out there! I hear some people complaining they are hitting 2″ groups at 100 yards instead of .75″, really? still sounds like a hit to me. How about it will never jam on you! Clean up is a breeze and it is built to last for decades. The Mini I have is from the mid-90’s, and it is stainless and wood, built like fort knox! It has never jammed – ever or FTE’d unlike the ARs, nor has ever been demoralizing to clean. I’ve hit everything I’ve aimed at, and dumping mags is intimidating, awesome! A total bad ass gun I would recommend to anyone to have by their side if SHTF.

  11. Are the barrel reciever and bolt of the mini14NRA chrome molly?..
    Could you humor an old soldier that has a mini14NRA I
    will give my son when I pass. I wanted to gather some
    facts about this SUBMOA rifle while the folks that made
    are it are still alive.

    Any help will be appreciated.
    US Army Jan 1964-December 1969
    Steve

  12. Are the barrel reciever and bolt of the mini14NRA?..
    Could you humor an old soldier that has a mini14NRA I
    will give my son when I pass. I wanted to gather some
    facts about this SUBMOA rifle while the folks that made
    are it are still alive.

    Any help will be appreciated.
    US Army Jan 1964-December 1969
    Steve

  13. IAre thee barrel reciever and bolt of the mini14NRA?..
    Could you humor an old soldier that has a mini14NRA I
    will give my son when I pass. I wanted to gather some
    facts about this SUBMOA rifle while the folks that made
    are it are still alive.

    Any help will be appreciated.
    US Army Jan 1964-December 1969
    Steve

  14. Very informative article. I was also under the impression that the main reason the military switched to the chrome lined barrels was to reduce not only the heat but the carbon build up as well. The combination of which was the cause for all the jamming and reliability issues the original M16 was having.

  15. Nice article, When you are giving data on barrel life to shots fired is this an average or is it based on low end quality materials. There is a great deal the rides on who manufactures barrels and the metal composition. Barretta was almost declined the military contract they have now based on metal formulations for their barrels.

  16. Your nice article on the mini 14 NRA ubder finish you listed Chrome-molly steel. Is the
    barrel made of that or is that a fonish on the bolt. I love my Mini14NRA about as much as
    anyone can love a metal object, but facts on this rifle are scarce and I have been trying
    to get some facts on it scince I bought it soon after it came out. There is also no spec
    sheet that ships with it. I hope your article was saying the rifle is Chrome-molly steel not
    just a plated bolt.

    Steve Blickley

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