To the naked, untrained eye, an AR barrel looks like one solid piece of metal. However, it’s actually TWO!

The barrel is threaded and the barrel extension is attached. The extension houses the feed ramps and is what sits inside the upper receiver in order to improve accuracy. The index pin sits inside the notch in the upper receiver to ensure the barrel seats properly.

Got some time to kill? Check out the patent application for the barrel extension here: http://www.patentsencyclopedia.com/app/20160010938

The barrel nut has a couple of functions.JB-BarrelNut-2T

For starters, it secures the barrel to the upper receiver. The barrel indexing pin fits into the indentation in the upper receiver and the barrel nut threads over top of the barrel, onto the receiver, in order to keep the barrel affixed to the upper receiver.

Secondly, the barrel nut allows the handguard – whether free-floating or drop in – to attach to the upper receiver. After securing the barrel nut to the upper receiver, most free-floating handguards attach to the barrel nut via allen keys or a company-specific wrench.

Finally, in the case of direct impingement, the barrel nut p_100009657_2holds the gas tube in place to allow the AR-15 to cycle properly. When a bullet is fired from the AR, the gas forcing the bullet down the barrel is pushed through the gas port, through the gas block, down the gas tube (which is secured to the upper receiver by the barrel nut) and helps to cycle the next round

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Also called “Flash Suppressor”, “Flash Guard”, “Flash Cone”, or “Flash Eliminator”.black-rain-ordnance-ar15-flash-hider

A flash hider is a device which attaches to the muzzle of a rifle that helps to reduce the amount of flash/light seen by the shooter while firing by cooling or dispersing the burning gases that exit the muzzle.

The main purpose of a flash hider is to lessen the flash that the shooter sees when the firearm is discharged. A common misconception is that it’s primary goal is to lessen the flash signature seen by the enemy when the gun is fired. Fhider_SG_KFH_BK_lg

Flash suppressors are very different from muzzle brakes! While they are both located/mounted in the same place on the AR, muzzle brake is used to reduce the perceived recoil a shooter experiences (and typically has zero to do with eliminating flash), while the flash suppressor only limits the amount of flash the shooter sees and usually does not affect recoil.

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According to Wikipedia:

Rifling refers to helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.

Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as “1 turn in 10 inches” (1:10 inches), or “1 turn in 254 mm” (1:254 mm). A shorter distance indicates a “faster” twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.

In layman’s terms, the lands are the raised spirals inside the barrel of your AR. The grooves are the “ridges”.

When the bullet travels down the barrel after being fired, it uses the lands and grooves to create spin (twist referred to earlier), which affects accuracy, distance, and trajectory.

Learn more about lands and grooves in our blog about Barrel Rifling by clicking here!

A good example of lands and grooves in a Royal Ordnance L7 Tank Gun.

A good example of lands and grooves in a Royal Ordnance L7 Tank Gun.

A muzzle brake or recoil compensator is a device connected to the muzzle of a firearm or cannon that reduces the amount of perceived recoil when the AR is fired, as well as helping to control muzzle rise after the firearm has discharged.

They are also used on pistols for practical pistol competitions, and are usually called compensators in this context.

Flash suppressors are very different from muzzle brakes! While they are both located/mounted in the same place on the AR, muzzle brake is used to reduce the perceived recoil a shooter experiences (and typically has zero to do with eliminating flash), while the flash suppressor only limits the amount of flash the shooter sees and usually does not affect recoil.

An excerpt from the FSD Blog, “Let’s Twist Again”:

In layman’s terms, the twist rate is the number of revolutions the rifling makes inside the barrel.

Think of a Slinky (younger folks, look it up). The spiraling of the toy is what it’d look like if you took away the outer metal of the barrel and only left the lands and grooves inside. You can stretch it out so that the spirals appear farther apart, or mash it together and the spirals will compact. The spirals in a Slinky are the revolutions we’re talking about.

Rifling

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The more times the spiral makes a full revolution, the lower the twist rate. For example, a 1:9 (to be read “one in nine”) twist rate means that, for every 9 inches, the rifling makes one complete revolution inside the barrel.

When it all comes down to it, we’re really talking about stabilizing bullets. That is, taking into account the air that the bullet must pass through and figuring out how long the bullet will remain stable.

The numbers of revolutions made inside a barrel determine the stability of the bullet. So, the lower the number, the more (and sometimes faster) the bullet is spinning, the more stable the bullet is.

You can learn more about Barrel Twist Rates via our blog by clicking here!