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What Does The Gas Block Do?

The AR-15 is a gas-operated rifle. It uses a direct impingement gas system, in which the expanding gasses from the barrel are redirected by the gas block, through the gas tube, and onto the bolt carrier gas key, which unlocks the bolt and allows it to move back, re-cocking the hammer for the next shot on the way back.

Shooting Competition

How Does The Gas System Affect Your Rifle's Performance?

The gas block is a vital part of the AR-15 operating system, and it can affect your rifle's performance in many ways. With non-adjustable gas blocks, the gas port's placement on the barrel and the gas port's size determine how the system will behave. For example, your system might be under-gassed if the gas port is too far from the chamber. As a result, the rifle may not redirect enough gas to cycle the gun reliably. On the other hand, if it is too close to the chamber, you may be letting too much gas into the chamber, which can damage the internal components of your rifle. Moreover, an over-gassed AR will also get dirty quickly because of the direct impingement operating system.

Now, you can find the optimal spot to place the gas block on the barrel depending on the barrel length and the caliber your AR is chambered in. However, the problem is that several factors can increase or decrease the level of gas circulating in your system, and a fixed, non-adjustable gas block cannot adapt to all of these situations.

For instance, if you are shooting subsonic ammunition, the redirected gas may not be enough to cycle the rifle, or if you add a suppressor, you may end up over-gassing your rifle. Both situations can cause problems for the reliability and effectiveness of your rifle.

How Does An Adjustable Gas System Work?

An adjustable gas block does not only redirect the gasses from the barrel to the gas tube but also acts as a valve, increasing or decreasing the size of the gas port to control the amount of gas that enters the system.

Adjustable Gas Block for Suppressed AR15

Why Is An Adjustable Gas System Better?

An Adjustable gas system is very practical. That allows you to adjust your gas setting on the fly and optimize your rifle for shooting in various situations. For example, if you are shooting low-powered ammunition, or your rifle has a lot of dirt and carbon build-up due to excessive use in the field, you can increase the amount of gas making it into the chamber. On the other hand, if you are using a suppressor, you can decrease the gas settings to compensate for the increased gas pressure.

Types of Adjustable Gas Blocks

Generally, there are two types of gas blocks that you can install in your AR rifle. Some can be adjusted dynamically across a spectrum, and some have pre-determined positions like open and restricted. Where dynamically adjustable gas blocks allow you more control over fine-tuning your gas system, those with dedicated positions are usually easier to adjust on the fly and work quite effectively.