What Size Gas Block Do I Need for My AR-15?

13th Jul 2020

AR-15s are some of the most customizable — and most popular — firearms on the civilian market. Countless parts are available for building a configuration made to your specifications, but they must be compatible to be effective. While some come down to aesthetics and your personal preference, others will have a direct impact on a gun's function and reliability. The gas block is a perfect example.

What Does a Gas Block Do on an AR-15?

On an AR-15, the gas block is mounted underneath the handguard between the upper and the front sight. This component sits over a hole in the top of your barrel. When you fire a round, a portion of the pressure moving the bullet forward travels up into the gas block and back toward the chamber through the gas tube. From the factory, most AR-15 gas blocks push the maximum amount of gas back through the tube, putting excess wear on your rifle and leading to heavy carbon buildup.

Choosing the Right Size Gas Block for an AR-15

Before you can improve your gun with a new gas block, you need to know what size to buy. When looking at a gas block online, you will see an inner diameter listed for the part, such as 0.750". This number corresponds to the width of your barrel and must match for the part to fit.

Most AR-15s have barrels in a standard diameter of 0.750". If you have a pencil barrel — a thinner, lightweight barrel carried over from the original M16A1 design — you will need a gas block with an inner diameter of 0.625". Similarly, most heavy or "bull" barrels will require a gas block measuring 0.936".

If you do not know your barrel size, save a trip to the gunsmith by measuring for yourself. To measure the diameter of your AR-15 barrel and determine the right size gas block for your gun, pick up a set of reliable calipers from your hardware store and measure the barrel in front of the existing block. Once you have your inner diameter, you can shop gas blocks to find one that suits your needs and aesthetic preferences.

Other Options to Consider When Choosing a Gas Block

In addition to diameter, you have other options to consider when choosing a gas block for your AR-15. These include:

  • Adjustable gas blocks: Upgrading to an adjustable gas block lets you compensate for changes in pressure when changing ammunition, helping to prevent overgassing and extending the life of your components.
  • Low profile gas blocks: If you have a free-floating rail system installed for greater customization and improved accuracy, you will probably want to install a low profile gas block to ensure proper fit.
  • Lightweight gas blocks: The deeper you get into customization, the more you need to consider the added weight of each upgraded component, especially if you use your AR in competitions. Lightweight gas blocks contribute less to the gun's overall weight.

Upgrade to a New AR-15 Gas Block

Wing Tactical is your source for gas blocks made to fit any AR-15 barrel and handguard configuration. Upgrade to one of our new gas blocks to gain better control over pressure in your gas system and prevent unnecessary wear on your gun's components. If you have any questions or need help choosing the right gas block for your AR-15, contact us today.

View Our Selection of AR-15 Gas Blocks