AR-15 Barrel Basics, Part I

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.

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.

[gzediker]