There are a few considerations to note when talking about barrel length. AR 15 Barrels come in lengths that range from as short as 7” all the way to 24” long. The most common barrel length is 16”. The ATF requires any AR rifle that contains a barrel shorter than 16” carries a Class III tax stamp. This means additional cost and headache to be sure you are legal.
The general rule for length requirements states the greater the distance you intend to shoot the longer the barrel should be. A longer barrel offers sufficient pressure to attain higher acceleration and provide increased accuracy. Longer barrels are more difficult to maneuver especially in close quarters.
Using shorter barrels makes it easier to maneuver in confined areas, but it comes with a trade off as adding one inch of length to a shorter barrel can result in a foot-per-second velocity increase of up to 200 feet. (The rate of increase begins to slow at 11 inches nearly disappearing at about 2o inches)
The Best overall length to start with if you need accuracy as well as maneuverability in one rifle is clearly a 16” barrel. But there are many other options to consider, let’s go over those one by one.
Cold Hammer forged vs. Mil-Spec Barrels
The vast majority of AR 15 owners can get by with a standard mil-spec barrel. Only very heavy users will require the greater long-term benefits of a cold-hammer-forged barrel. Cold hammer Forging entails a process that uses a large hydraulic hammer press to hammer the barrel blanks from multiple sides. This makes the rifling a compression around a mandrel rather than button rifling as per mil-spec. This produces a tougher, more durable barrel with a longer lifespan that performs better especially when hot from use.
Because there are only a few cold hammer machines, as well as the added time it takes to manufacturer, the cost is higher.
The profile of a barrel actually refers to the weight of the barrel. Profiles are seperated into three basic categories: lightweight, government, and heavy. One thing to consider is the heavier the barrel, the greater the resistance it provides to the buildup of heat when firing. A heavier barrel will last longer than a lighter one. This fact makes it a better choice for frequent AR-15 users that have no weight concern. On the other hand, a lighter barrel makes the gun easier to carry, make ready, and control. The M4 government profile is the most popular option. It offers an acceptable compromise of weight and maneuverability.
Interior: Chrome vs. Stainless-Steel
Mil-spec AR-15 barrels typically include a lining made of chrome poly steel. The chrome lining is beneficial for use in high-humidity and saltwater environments as it offers improved resistance to corrosion. The chrome also protects against friction reducing heat, helping to extend barrel lifespan. Chrome barrels are thought to be easier to clean as well.
The convenience of cleanliness does not come without any disadvantages, however. Chrome lined barrels can reduce the accuracy at long distances. This is due to multiple issues that occur during plating. The first is chrome coating unevenness that results in high points within the barrel, that can cause compression losses. The second is lessoned rifling after coating the barrel, causing slightly less projectile rotation. Keep in mind, the loss of accuracy typically occurs at distances over 300 yards, which means the vast majority of recreational shooters will not be impacted.
A stainless-steel barrel, also called a “match barrel,” does not normally contain a chrome lining. This provides increased accuracy at longer ranges. For occasional to moderate users there is little worry of the slight increased chance of wear or corrosion if properly maintained.
The cost variance between these barrels is minimal so decide which you need based on necessity rather than potential savings.
Twist rate refers to the rifling inside the barrel that causes the bullet to rotate before exiting. The Twist Rate of the barrel describes the number of rotations a bullet will make in relation to the number of inches it travels within the barrel. For example, a 1:7 twist rate means that the bullet must travel 7” to make one complete rotation. A barrel with a 1:7 twist ratio enables a bullet to spin faster than one with a 1:9 or 1:12 ratio. A faster rotation results in greater bullet stability as it travels through the air. A 1:9 twist ratio is the most common.
There are several things to consider before choosing a twist rate. The weight of the bullet is a consideration. Popular recommended twist ratio to ammo grain combinations are:
1:9 = 40, 45 & 50 grain
1:8 = 55 & 62 grain
1:7 = 75 & 77 grain
*See our Twist Ratio Chart for a clearer visual
Watch the video for an explanation that has visual examples and a walk through of the differences.