How To Tune Your AR-15 Gas System

Posted by Frankie Chan on 23rd Feb 2023

There is an astronomical performance difference exists between a properly tuned AR and one that is not. In any gas-operated firearm, the gas system is responsible for cycling the action and chambering a new round after each shot. If the gas system is not functioning correctly, the weapon may experience malfunctions, such as failure to feed, failure to extract, or excessive recoil.

If you are building an AR, setting up your weapon for competition, or want your weapon to run smoother, you need to understand how the gas system works in an AR-15. This post will discuss the AR-15 gas system and how you can tune it for the best performance, accuracy, and reliability.

What Is In The Gas System

The gas system plays a critical role in the functioning of any gas-operated firearm. Most common semi-auto weapons, like the AR-15 and AK-47, are gas operated. This means the gas pressure created from a round fired inside the chamber is used to cycle the firearm.

There are multiple types of gas systems used in different rifles. For example, rifles like the AK-47 and its variants use a long-stroke piston-operated gas system, whereas other rifles like the SKS have a short-stroke pistol-operated gas system.

Most AR-15 utilize the direct impingement gas system. The gas system consists of multiple parts, which work in unison to operate the rifle. Here are some of the main parts you need to know about, so you can decide which part needs to be replaced.

Gas Block:

The gas block on the AR-15 serves as a junction between the gas system and the barrel. It captures the gasses produced when a round is fired and redirects them back into the rifle's action.

Gas Tube:

After the gas block captures the gas, it travels through the gas tube. Finally, the gas tube delivers the gas straight into the gas key, pushing on the bolt carrier group, unlocking the bolt, and cycling the rifle.

Bolt Carrier Group:

The bolt carrier group is one of the essential parts of an AR. It moves back and forth in the receiver with the gas and buffer spring pressure. As it moves back under the gas pressure, it extracts and ejects the spent casing from the chamber, and on its way back, it strips a round from the magazine and chambers it.


The buffer, located at the end of the buffer spring, absorbs the energy of the moving bolt carrier group as it moves back, slows it down, and then returns it to the forward position. The buffer can come in different weights, affecting your rifle’s performance. For example, heavier buffers can reduce felt recoil, whereas lighter buffers can increase the cycling speed of your weapon.

Buffer Spring

The buffer spring is compressed inside the buffer tube as the bolt carrier group moves back. This absorbs some of the recoil and provides the necessary tension to slow down the bolt carrier group and send it back forward.

The strength and tension of the buffer spring significantly impact when tuning your weapon. For instance, heavier buffer springs provide more resistance to the bolt carrier group's movement, and lighter ones allow faster cycling and performance.

Reasons To Tune The Gas System

Tuning your gas system can result in a significant increase in your weapon's performance, and it can help you fix several issues and malfunctions as well. Here are some main reasons you may want to tune your AR-15 Gas system.

Improve Reliability:

Tuning the gas system involves adjusting the flow of gas into the bolt carrier group to achieve optimal cycling speed, which results in improved reliability. As a result, a properly tuned rifle is more comfortable to shoot and has significantly lower chances of experiencing malfunctions like failure to feed and extract. Moreover, too much gas pressure can damage various parts of your rifle. Therefore, a properly tuned gas system also improves the longevity of your rifle.


Over-gassed occurs when too much gas is returned to the bolt carrier group. This can cause the rifle to cycle too fast and generate excessive recoil. Below are the common issues caused by an over-gassed weapon:

  • Causes malfunctions such as failure to extract, eject, and feed.
  • Cause the bolt to unlock early and decrease the pressure in the barrel, which leads to reduced bullet velocity.
  • Increased wear and tear on the rifle's internal components
  • Excessive carbon buildup
  • More violent recoil
  • Increase muzzle rise
  • More hot gas blowback into the shooter’s face


Under-gassed occurs when too little gas is directed into the bolt carrier group. The gas pressure may not be enough to cycle the rifle, which can cause ejection and other feeding issues.

When the bolt carrier group does not move back completely, it can't eject the spent casings or load new rounds. As a result, under-gassing can seriously decrease the reliability of your rifle, and tuning your gas system can help you prevent these issues.

A simple way to determine if your weapon is over-gassed or under-gassed is to look at where is your brass ejection. The optimal position is between 3 to 4 o’clock.

Reduce Recoil And Muzzle Rise

If the gas system is not set up correctly, whether because of excessive gasses, or light buffers, it can have a very violent recoil impulse and a lot of muzzle rise. This can make it very difficult for shooters to be accurate, especially when shooting at a high-speed rate. Tuning your gas system helps prevent excessive recoil and results in a smooth shooting, accurate and reliable firearm.

Using A Suppressor

Using a suppressor will require changing the gas system setups. The suppressor increases the length of the barrel and keeps the expanding gasses inside the rifle for longer before they are expelled from the muzzle. Moreover, Suppressors work by directing the gasses into small baffles, increasing the pressure inside the barrel. All this pressure means more gasses enter the gas block and impact the bolt carrier group through the gas tube. However, if your rifle is properly tuned to run with a suppressor, these over-gassing problems can be avoided.

Way To Tune The Gas System

Install An Adjustable Gas Block

Installing an adjustable gas block on your rifle is one of the best ways to tune it easily. As the name suggests, an adjustable gas block allows you to adjust the amount of gas that enters the gas system. This can help you prevent over-gassing issues. Moreover, it makes your rifle more versatile. For instance, if you are using the suppressor, you can decrease the amount of gas entering the chamber. Similarly, if your rifle is dirty, you can open the gas block and let more gas into the system.

Change The Bolt Carrier Group

You can also tune your rifle using  bolt carrier groups with different weights and finishes and pair it with the appropriate buffers and buffer springs. So, to tune your rifle, you should get a high-quality bolt carrier group with the proper buffer spring and buffer.

Change The Buffer Weight

The weight of the buffer also affects the rifle's cycling and reliability. Therefore, it can be switched out to tune your rifle’s performance. For example, heavier buffers can reduce felt recoil and improve cycling reliability on an over-gassed weapon.

Install A Proper Buffer Spring

The buffer spring affects the force required to cycle the rifle's action. Therefore, it must offer enough resistance to absorb as much recoil as possible and offer the bolt carrier group enough tension to move forward into the battery reliably.

Adjust The Gas System According To The Ammo

Lastly, the kind of ammunition you use can also impact the cycling of your rifle. For instance, if you tune your rifle using regular FMJ rounds or rounds with a specific projectile weight, your rifle may get a little finicky when using subsonic or high-pressure cartridges. So, the weapon should be tuned depending on its intended use. For example, you can set up your gas system to that specific ammo for a competition rifle that will only be shooting match-grade ammunition. However, a general-purpose rifle should be able to work reliably with a wide range of ammunition types and tuned with higher tolerances.

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