What Size Gas Block Do I Need For AR15

In an AR-15, the gas block sits neatly underneath the handguard, positioned right above a strategically placed hole atop the barrel. Most AR-15 rifles have the 0.750" diameter gas port barrel.

Here's how it works: when you fire a round, a portion of the gas produced zips back through the gas tube and travels back into the chamber. This is a crucial part of the rifle's operation. 

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How to Pick the Right Gas Block Size for Your AR-15

remove a2 front sight gas block

When you're in the market for a new gas block for your firearm, it's crucial to match it to your barrel's diameter. Typically, you'll encounter gas block sizes denoted in inches, like the common 0.750". This measurement should correspond to the width of your barrel to ensure a proper fit.

Based on School of American Rifle's teaching, when it comes to gas efficiency and bolt travel speed. The tightness of the gas block around the barrel seal is also a factor to prevent leakage. 

The same goes for the gas pressure around the gas ring and bolt tail. So this means the buffer system and the bolt carrier group are also important parts.

Any leakage around these areas can affect the rifle's operation besides just picking the buffer weight and the buffer spring.

ar15 gas blocks

If you have a barrel that's on the slimmer side, reminiscent of the vintage M16A1, you'll be looking for a 0.625" gas block. On the other hand, for those beefier, thick-barreled rifles, a 0.936" gas block is your go-to.

Gas Block Considerations

Adjustable Gas Blocks

adjustable gas block

Adjustable Gas Blocks allow you to tweak the amount of gas that cycles through your firearm, especially when you're using various types of ammunition especially when shooting suppressed. This flexibility can be a real game-changer in preserving the lifespan of your gun's components. It's like having a customizable setting for different shooting scenarios.

Low Profile Gas Blocks

low profile gas block ar15

Thee low profile gas blocks are very popular for AR15s with free float handguards. Because they fit snugly under those rails without any contact with the rail, and it provides a seamless integration that doesn't mess with your your firearm. It's all about maintaining that perfect balance between functionality and form.

Lightweight Gas Blocks

lightweight steel ar15 gas block

These are a top pick for competitive shooters. In shooting competitions, every ounce counts. Opting for a lighter gas block means your rifle won't be weighed down, giving you that slight edge in speed and maneuverability.

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