AR-15 Barrel Basics, Part I

AR-15 Stainless Chromoly Rifle Barrels by Glen Zediker

The barrel is truly the make-or-break accuracy component in any rifle. There are contributing factors that also have to be correct, but the difference between a rifle that shoots well and one that shoots very well is in the barrel.

The standard for “shoot well” is ultimately subjective. The use a rifle is put to, and, mostly, the distance the bullet covers, helps each shooter set his own standards for accuracy. I expect my competition rifles to group no bigger than 4 inches at 600 yards, and that’s a 10-shot group fired prone with a scope. Half-inch 100-yard groups don’t impress me, and that’s because half-inch 100-yard groups are NOT 3-inch 600-yard groups. They’re bigger than that.

If you want to get best accuracy, you really do get what you pay for in a true match-grade barrel. One reason is that there’s not really a definitive standard, beyond those established by the barrel maker, for “match-grade.” I say a match barrel is one that wins matches. Experienced competitive shooters become aware of this because we will go through several barrels, and therefore see a performance pattern develop barrel to barrel. We want that pattern to be a flat line. All of them good, none of them bad. We also tend to get attached to different brands, and that’s from the old “If it ain’t broke…” way of thinking. Truth is that there are options in truly great barrels, they just each tend to have followings, so it depends on whom you ask.

As suggested, it’s distance that really shows differences in barrels. Take a rifle with a decent barrel and one with a great barrel to the firing line and then keep moving farther and farther from the target. There will be less notable differences in these barrels at 100 yards. There will be more at 200. More still at 300. Way more at 600. And night and day at 1,000. I’ve seen this too many times to respect it with a “maybe.” It is also, therefore, why many people may be entirely happy, and for good reason, with a less expensive barrel.

It’s kind of hard to recommend the five bills or so (turned, outfitted, chambered, installed) that a barrel from the “top tier” will cost. There’s another step down from these that few people will find fault with. That is also not to say that a barrel that costs half that much won’t shoot as well as the very most expensive; it is to say, as already hit upon, that it’s the barrel-to-barrel-to-barrel consistent performance level that defines the “best” barrel makers.

If you are building up an AR-15 and want to see it shoot just as well as it can, you dramatically swing the odds in your favor by purchasing a Krieger, Lilja, Obermeyer, Schneider, Satern, Bartlein or other similar brands. Those barrels, as is true with many from custom barrelmakers, aren’t graded. There’s only one standard with these makers: it’s good enough to sell, or it goes in the trash.

The next tier are those that are graded, after manufacture, and segregated by their measured quality. Again, different standards apply and none are universally followed, but dimensional consistency and correctness and straightness are the leading indicators. Pac-Nor, Shilen, Wilson, and Douglass come to mind. The best of those are frequently as good as custom barrels.

What makes a good barrel good? As mentioned, straightness and end-to-end consistency of bore and land diameters are the main influences. Consistency of the twist rate from end-to-end and interior finish are also important. In a truly custom barrel, the maker takes steps to ensure all these elements are the best they can reasonably be.

There are differences in barrel manufacturing methods, and the leading one is how the lands are formed. They all start with a drilled piece of round steel, drilled to land diameter; it’s the grooves that are displaced in these processes. Most rifling is done via a button that’s pulled through the drilled blank. It’s a swaging process. This button turns as it goes, and the better makers use a controlled leade to bring it on. That helps improve twist rate consistency. Another style is cut rifling, and that is a machining operation whereby a single-point cutter is driven through the drilled blank, cutting one groove at a time. This can be precisely controlled, including profile contouring on each land.

Note: There are actually five different methods for introducing rifling to a bore, but these two are really the only means found in competition-use barrels.

There will always be arguments about which is best. As with any metalworking, finished quality ultimately comes down to tool precision and operator standards. Other perks in a custom barrel usually (and certainly should) include hand lapping and stress relieving. The lapping smoothes the interior surface and also improves dimensional consistency. The stress-relieving helps ensure that the barrel “looks” in the same direction after it gets hot. That, by the way, is how we can get a barrel with a smaller outside diameter to shoot as well as one that looks like a Red Bull can.

The number of grooves is another point of difference not all agree on. An odd number of grooves is thought to reduce stress on the bullet because there are no opposing contact points. The fewer grooves, the more shallow the angle of engagement is, and that’s thought to be a good thing. Some think that the more grooves, the less contact, and the more balanced “support” the bullet has. There are 3-, 4-, 5-, and 6-groove barrels that all shoot well! For what it’s worth, the barrel I tend to use has four grooves and is cut-rifled.

The Question of Hammer Forging

This is a process whereby the interior is formed by forging the barrel over a mandrel. Forging is essentially beating the fool out of the outside of the barrel until it conforms to the mandrel inside; the mandrel has a mirror image of the rifling. Barrels produced with this method are available for AR-15s. It’s not known as a viable means of attaining on-target greatness, despite some claims I’ve heard. Mass-produced and mil-spec barrel are routinely hammer forged. I personally don’t know of anyone who has won a tournament with a forged barrel, but I also cannot personally say you wouldn’t be thrilled with one.

What About Chrome-Lined barrels?

A lot of AR-15s have chrome-lined barrels. This is done to increase longevity. It also provides corrosion resistance. Chrome-lined barrels are dimensioned to allow for the application of the chrome layer. Thus, it’s very unlikely to maintain superior dimensional consistency, if you think about it. Now, that’s not to say it’s a bad barrel. I’ve had Colt HBAR barrels that shot as well as all, and I’ve also had them that shot minute-of-washtub. I will say it’s not a choice for anyone looking to build up a rifle he expects small groups from. It is a good choice for anyone else. They do, indeed, last a while.

What do you think makes a good barrel? Tell us in the comment section.


About the Author:

Glen Zediker

Glen Zediker is the owner of Zediker Publishing, which specializes in books and other publications focused primarily on AR-15s, handloading, and shooting skills. Since 1989, he has authored or co-authored 20 books.

He started shooting at age 5 and competing in NRA Smallbore rifle at age 8. He got his first AR-15 at age 15 and has now had 45 years of experience with that firearms platform. He’s worked professionally with some of the greatest shooters on the planet and leading industry professionals. And he does pretty well on his own! Glen holds a High Master classification in NRA High Power Rifle and first earned that using an AR-15 Service Rifle. He’s also competed in many other forms of competition, including USPSA, Steel Challenge, Silhouette Rifle and Pistol, Bullseye Pistol, ISSF Air Rifle, Practical Rifle and shotgun sports.

Since 1986 Glen has been a frequent and regular contributor to many publications, having had over 500 assigned articles published. See more at
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Comments (16)

  1. Wow! That’s real news! I also think that I remember seeing gain twists being used in the lighter caliber field artillery pieces, maybe in the late 1800’s and on up through WWI…don’t know for sure. My only real concern with a gain twist would be a potential increase in copper bore fouling due to the additional bullet engraving being done…but maybe there’s real data somewhere (at the barrel makers, for sure) that could factually speak to that issue, as well as to any detrimental effects on a fired long range match bullet…if there are any.

    1. Progressive twist barrels are thought of as Old School & European Military…they were frequently referred to as ‘gain twists’. A barrel might start out at 1-10 twist just in front of the chamber and steadily ‘gain’ in twist rate as it progresses toward the muzzle end, where it might be as fast as something like 1-8. I think that the Italian Carcano military rifles (and just a few others) had this type of rifling. I can only guess at the ballistics reasoning behind this gain twist (chamber pressure peaks, throat erosion compensation, etc???). I doubt anybody manufactures using it in the modern era.

    2. There are a number of custom barrel makers who produce gain / progressive twist barrels. I have a Bartlein gain twist I use for F-Class and it shoots great. They are more expensive due to the additional work and special rifling machine needed to manufacture them.

    1. Joe, the “forend” or “handguard” is probably along the lines of the DPMS National Match Free Float. It doesn’t look floated but, take a look under the hadguards. Neat design.

    2. Ryan, correct. It looks just like the DPMS National Match ‘legal’ free-float
      job that A Bruce Dow did for me many years ago when re-barreling a Colt’s A2 with a 6×45 Lilja stainless HBAR match barrel. He is an expert competition service rifle builder / smith. It’s really sneaky how they can seem to completely hide that float tube under stock type hand guards and stay the width of a hair off of any barrel mounted component…very effective, too.

  2. Excellent writeup on barrels!
    Barrels are truly the heart of a rifle….there are many other factors that can improve accuracy, but it all starts with a well made and mounted tube.

  3. A very interesting article! The match grade barrels discussed are something outside my experience. I would be interested to know, where nitrided barrels (sometimes referred to as Melonite) fit within the taxonomy presented.

    1. Same here. Nitrided barrels are slowly making gains in the market but there seems to be little comparison data available. Especially in the areas of accuracy and longevity.

    2. The deal with nitride barrels is similar to that of the chrome lined (plated) bore. They might bring an improvement in accuracy over chrome due to (maybe) improved application consistency along the bore interior, but most claim to have measurably improved longevity parameters over chrome (but not vast)…but I think that process is relatively young compared to the chrome lining and we’ll just have to see where a large sample of real-world data places any benefits.

  4. Most people unless they are extremely good competitive shooters will not benefit from custom barrels unless they are shooting a bullet weight that is not compatable with a barrel twist or the barrel is extremely bad.. I have found that spending money on practice ammo and obviously glaring problems like really bad triggers and loose bedding etc. can improve a guns performance a lot and is not very expensive in comparison to new barrels etc. most people do not shoot to the ability of their rifle or pistol without alot of practice. Includes me a club shooter for years.

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