As rifles have become a more popular option for home defense and even just recreational shooting, a lot of people are looking for information about the technical aspects. Understanding something like an AR-15’s barrel length and twist rate can be daunting, so let’s try to demystify it a bit. The barrel length and twist rate options of an AR-15 are arguably two of the most important variables to consider when making your choice. Sure, cosmetic preferences such as stock, hand guard, and finish are important; but understanding the nuances between barrel length and twist rate is the key to understanding the performance you can expect from your rifle. Get ready to dive into the world of AR-15 barrel length and twist rate – here’s what you need to know!
What is AR-15 Barrel Length?
When it comes to AR-15s, one of the key aspects to consider is barrel length. This is because both accuracy and terminal ballistics are affected by the length of the barrel. Let’s take a look at what affects barrel length:
Most agree that shorter barrels are often better for using in confined spaces like in buildings or close quarters – where maneuverability can be more important than maximum accuracy. The longer the barrel, the more front-heavy an AR-15 will become and the less maneuverable it will be in tight spaces. Most rifle cartridges have their peak velocity at somewhere between 16-and 22-inches; as such, anything shorter than 16 inches usually won’t see any, or only minimal increases in velocity over typical lengths.
A longer barrel creates greater accuracy potential and increased shot distance. That’s because they allow bullets to reach their highest speeds while maintaining stability, due to the added rifling – meaning the bullet spin increases accuracy while moving downrange. This can also result in a flatter trajectory causing above average drop off distances with certain weight projectiles that might not be possible with shorter barrels. Most manufacturers tend to carry barrels in lengths ranging from 10 to 24 inches, giving shooters plenty of options for finding their perfect balance between mobility and accuracy.
The Effect of Barrel Length on Accuracy
When discussing the effect of barrel length on accuracy, there are two prevailing views that have been widely debated. The first belief is that shorter barrels will affect accuracy negatively due to their reduced sight radius and faster barrel whip – the barrel’s tendency to flex as it rotates when fired. Proponents of this point of view argue that these factors can make sighting in more challenging and lead to decreased accuracy at longer distances.
Other experts believe that barrel length has little to no real effect on accuracy. This camp argues that since most AR-15 rifles are chambered for .223/5.56 caliber rounds, which generally need a relatively short barrel anyway, any increase or decrease in barrel length won’t result in improved accuracy. This is because the lighter weight projectiles used with these rounds are largely unaffected by air resistance and current AR-15 designs are more than enough to stabilize even long bullets used in heavier calibers.
Though both sides of the debate have valid arguments, many in the shooting community tend to agree that longer barrels can offer greater accuracy, provided they’re properly constructed and maintained. A 20-inch heavy contour barrel can usually provide better shot groupings over distances greater than 600 yards as compared to shorter barreled rifles or carbines due to its greater sight radius and increased stability. Its slightly harder steel construction also helps reduce excessive heat buildup which in turn improves accuracy compared to shorter barrels due to less fouling from coppering the bore.
Longer Barrels for Greater Accuracy
Longer barrels can also improve accuracy as they allow the bullet more time to spin properly and to stabilize. While a 14.5” barrel will produce a greater velocity, this is counterbalanced by accuracy due to its shorter length. Increasing barrel length even slightly can result in improved accuracy, with the best results being achieved with barrels 20-24” long.
Many weapons experts view increased accuracy as an important factor when selecting a weapon, and in many cases, accuracy is far more important than small gains in velocity provided by a shorter barrel. For hunters, target shooters, and military or police personnel shooting at sniping ranges or from relatively fixed positions, longer barrels can make a significant difference in precision. In addition to providing additional time for the bullet to spin and stabilize, longer barrels also can increase muzzle velocity which makes it easier to hit distant targets accurately.
When looking at the debate between short vs long barrels for increased accuracy, it is important to consider that most AR-15 users will not be using their weapons for sniping or extreme-distance target shooting. For users shooting at closer distances, velocity matters less and accuracy provided by a longer barrel matters more. If you are primarily looking for faster muzzle velocity from your gun then shorter should be your go-to choice.
No matter what you end up choosing, accuracy should be a top priority when selecting an AR-15 and it’s important to still consider the potential gains in precision that come with longer barrels versus the quickening of velocity that comes with shorter ones. As with most decisions involving firearms selection and use, recognizing your needs in terms of distance and application are key when evaluating whether longer barrels provide better accuracy than short variants.
Short Barrels for Increased Velocity
Once the commonly accepted reasoning that a longer barrel improves accuracy is understood, it is worth discussing the potential benefits of short barrels. It stands to reason that when the length of the barrel is reduced, so too is the distance that the bullet must travel before exiting the muzzle. This in turn can increase velocity resulting in enhanced accuracy at short distances. Short-barreled AR-15s are easier to maneuver and conceal than models with longer barrels.
When considering short barrels for increased velocity, there is still much debate over how much it actually affects performance. Some experts argue that reducing barrel length from 20 inches to 16 inches has no substantial effect on overall velocity and accuracy. Others suggest that when properly balanced with appropriate twist rates, significant increases in velocity can be achieved even with a reduction in overall barrel length. Whatever opinion one holds on the matter, testing will be necessary to arrive at any definitive conclusion on this topic.
When striving for the most accurate shots possible, it is essential to experiment with different combinations of barrel lengths and twist rates to find what works best for your particular firearm and shooting style. And it should be noted that while short barrels may improve velocity, other factors such as ammunition, gas system length and quality of components also come into play. With all these variables factored in, the overall accuracy potential of the weapon should become increasingly clear.
Other Factors Affecting Accuracy
When it comes to accuracy, the AR-15 barrel length and twist rate are significant factors, but they are not the only ones. Other important elements, such as bedding of the stock, gas system design, sight optimization, weight of the projectiles used, and even shooter skill level may have a major effect on precision.
While proper bedding of the stock will not increase velocity like a shorter barrel can, it can theoretically enhance accuracy. Lighter projectile weights typically result in less felt recoil and greater velocity than heavy or supersonic bullets which may help with accuracy–as long as shooting skill level is taken into account. Properly tuned gas systems are essential for optimal functioning and so too is an accurate sight that has been properly zeroed by the shooter. Both of these will contribute significantly to maintaining accuracy when weapon cycling and placement of shots on target.
Twist Rate and Projectile Type
The twist rate of the barrel and the type of projectiles being fired directly correspond with one another when it comes to accuracy. While the most common “optimum” twist rate established is 1:9, there are other spin rates that may work better depending on the projectile size and its corresponding weight. A higher twist rate such as 1:7 or 1:8 works best for rounds containing heavier bullets such as those used in long-range shooting while a lower twist rate would be ideal for lighter weight 5.56 NATO bullets or similar type rounds.
A higher twist-rate results in greater accuracy due to its capability of spinning faster which gives it more stability when it leaves the barrel and moves through the atmosphere at higher velocities. An increased spin helps keep the bullet more centered during travel so a better grouping of rounds can be achieved. Some experts argue that a slower spin is just as effective as a faster spin but instead of having more stability, accuracy is gained due to its improved ability to reach greater distances.
If you’re using heavier rounds and attempting to shoot at longer ranges, you can improve accuracy by ramping up your twist rate which will help stabilize your round and ensure that it maintains its center point throughout transit. If you’re choosing lighter round cartridges, then keeping your twist rate at 1:9 or even lower could be beneficial since it would increase the range without taking away from your accuracy since it would maintain its path throughout its transit.
- The average barrel length of an AR-15 is 16 inches.
- The typical twist rate for an AR-15 barrel is 1:7, meaning that the bullet will make one full rotation in 7 inches of barrel length.
- A study conducted in 2020 found that in some cases, a slower 1:8 or 1:9 twist rate was more efficient than a 1:7 twist rate when firing heavier bullets.
What is the Best Barrel Length/Twist Rate?
When it comes to choosing the best barrel length/twist rate for an AR-15, the answer is not as black and white as one would think. It depends on the intended use of the firearm and what type of projectiles the shooter plans to use beyond just traditional FMJ ammo. Longer barrels increase velocity, lower noise signatures, and allow for greater accuracy potential whereas shorter barrels provide easier maneuverability in confined spaces and less weight while sacrificing velocity. Selecting a barrel length/twist rate specifically designed for specific projectile types can greatly improve overall efficiency and accuracy of an AR-15 rifle.
Some may argue that 16″ is the ideal barrel length for any type of projectile since this is the most popular option offered by several manufacturers; however, due to federal regulations stipulating rifle barrel lengths must exceed 16″, some shooters may choose 18″ to 20″ barrels for more improved characteristics such as ballistics stability with heavier grain projectiles and projectiles with slower rates of twist.
Others may prefer shorter barrels such as 10″ or even 8″. While these barrel lengths do sacrifice some velocity, they make up for it with superior maneuvering capabilities in close quarters or heavier grain bullets that need less twist per inch than those requiring higher grains. Shorter barrels help offset weight issues particularly when riding an ATV or negotiating tighter spaces when hunting or even target shooting.
There is no right or wrong answer as to what is the best barrel length/twist rate for every application; rather, it boils down to personal preference and desired effects that can be achieved. Although there are tailored solutions based on particular projectile types and sizes, ultimately selecting the optimal barrel length/twist rate requires careful consideration from the shooter so that their AR-15 can operate at its peak performance levels.
Captain Hunter is a seasoned hunting mentor with over 20 years of experience in the field. His passion began as a young man on trips with his father and grandfather in the Colorado mountains. Today, he shares his unmatched skills in survival, tracking, and marksmanship through his website CaptainHunter.com. When he's not volunteering with youth hunting programs, you can find Captain Hunter providing expert hunting tips, gear reviews, and answers to your most pressing questions. His decades of experience make him the trusted guide to help any outdoorsman master the sport.