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In this section, we’re examining an important metric that measures a gun’s performance – velocity!
We’ll explain the various factors that determine a gun’s velocity, and give you a comprehensive chart for understanding how velocity is impacted by barrel length.
Let’s start with the basics:
What is Muzzle Velocity?
Muzzle velocity refers to the speed of a bullet as it passes through the muzzle of a gun. The muzzle is the end of a gun’s barrel.
As you might imagine, muzzle velocity varies quite widely depending on the type of gun you are shooting. Even within AR-15s, muzzle velocity might be very different from gun to gun. Since the AR-15 rifle is such a highly customizable gun, there are various features you can change which impact muzzle velocity, and we’ll examine them below.
AR-15 Barrel Length Velocity Chart
Velocity is heavily determined by the length of the AR-15’s barrel. It’s not an exact science, because other factors influence the velocity as well. Below we’ve included a chart so that you can have a rough idea of your AR-15’s velocity based on its barrel length:
How to Measure AR-15 Barrel Length
Most of the time, a gun’s barrel length will be marked when you purchase it. It is one of the main features of a barrel and will be prominently displayed. If you can’t find it, look for any product identification numbers on your barrel and do a quick Internet search.
If you still can’t find it, take your unloaded AR-15, and stick a rod down the barrel as far as it can go. Mark the rod, and measure the distance from the mark to the end. This will be your barrel length.
Does Barrel Length Matter When Shooting an AR-15?
Yes, barrel length matters and will make a noticeable impact on your AR-15’s performance.
Firstly, barrel length impacts a bullet’s velocity. Typically, longer barrels mean higher velocity. This is because the bullet is impacted by more pressure traveling the length of the barrel, and will leave the gun with more velocity.
Does Barrel Length Affect Accuracy?
Higher velocity tends to lead to more accuracy because the bullet can travel in a straight line more efficiently. Of course, this also heavily depends on the shooter’s skill, and can also be impacted by the twist rate of the barrel.
What Factors Impact the Velocity of a Bullet?
Simply put, many factors impact the velocity of a bullet. Here are some of the main ones:
Barrel Length
As mentioned above, barrel length impacts the velocity of a bullet. Longer barrels usually mean more velocity. The bullet is impacted by more pressure along the length of the barrel, picking up more speed, and resulting in a higher muzzle velocity.
Barrel shape and design will also impact velocity. The interior grooves and contours will affect the bullet as it leaves the gun, resulting in less or more velocity.
The Projectile
The mass and length of the bullet also influence a bullet’s velocity. The shape of the bullet might cut through the air more efficiently, resulting in a higher velocity. Generally, larger bullets result in lower velocity, because it requires a lot more energy to shoot them out of the gun.
Propellant
The quality and amount of propellant make a big impact on velocity. AR-15s operate with gas systems. The amount of pressurized gas will greatly impact a bullet’s velocity. Of course, more pressurized gas, used more efficiently, means more velocity.
As you can see, it’s complicated! Velocity is affected by many different features working in tandem.
Barrel Length vs Velocity - How Do They Affect Each Other?
As we explained above, longer barrels tend to mean more velocity, but this isn’t always the case. A longer barrel often provides more time for a bullet to generate velocity, as it is powered through the barrel by pressurized gas.
However, barrels are also designed differently, with different interior materials, shapes, contours, and twist rates. This can have a big impact on AR velocity and might be a reason that two similar length barrels have a different velocity.
That being said, you have to take it on a case-by-case basis. It’s still a good general rule that a longer barrel gives you more velocity, and you can use our chart above as a reference.
Conclusion
Thanks very much for reading our guide to AR velocity and barrel length. As you can see, there is a strong correlation between the two, but it isn’t always exact. A bullet’s velocity is determined by many factors, with barrel length being just one of them.
People Also Ask
Before we wrap up our article, let’s check out some of the most frequently asked questions about the AR-15.
What Length Barrel For AR-15?
The most common barrel sizes are between 16”-24”.
What Size Threads on AR-15 Barrel?
AR-15s most commonly use a 1/2x28 thread pitch.
What is the Shortest Barrel Allowed On an AR-15?
In most states, the shortest allowed barrel is 16”.
However, certain tax stamps can get around this in some States. Additionally, you might be able to add a muzzle to a shorter barrel to extend it to this length.
How Fast Does an AR-15 Bullet Travel?
It varies depending on many of the factors we mentioned in this article. An average speed is around 3000 feet per second.
On an AR-15, How Many Different Calibers Can You Build in Order of Velocity?
An AR-15 supports many different calibers. You’ll have to check the details of your barrel to see what is supported.
What is the Muzzle Velocity of an AR-15?
It varies depending on all the features mentioned in this article.
What is an AR-15 Effective Range?
Of course, it varies depending on velocity and accuracy, but usually around 400-600 meters.
How Much Velocity Do I Lose If I Shorten the Barrel On My AR?
It depends not only on barrel length but other factors as well. Check our handy chart above for a rough guide to this.
Does Twist Rate Factor in On an AR-15?
Yes, definitely. Different barrels offer different twist rates. The most common rate is between 1:7 and 1:9, but there are also twist rates outside this.