AR15 Thread Pitch: What You Need to Know

If you own an AR15 rifle or plan to buy one, you might be wondering what thread pitch is attached to the barrel and why it matters. Thread pitch is the distance between the threads on a screw or a barrel, measured in millimeters or inches. Thread pitch affects the compatibility of muzzle devices, such as flash hiders, muzzle brakes, suppressors, and compensators, that can be attached to the barrel.

In this article, we will explain the common thread pitches for AR15 barrels, how to identify them, and how to choose the right muzzle device for your rifle.

Common Thread Pitches for AR15 Barrels

Currently, there are two known standard thread pitches for an AR15 barrel:

1/2x28, for a standard mainstream (M4) AR15 /5.56 NATO and .223

5/8x24, for other builds or purchased AR15s in 300 Blackout caliber

The AR thread pitch attached to an AR15 barrel is one of the most commonly asked questions.

However, these are not the only thread pitches that exist for AR15 barrels. Some manufacturers may use different thread pitches for different calibers or models of rifles. For example, some 9mm AR15s may use 1/2x36 or 1/2x28 threads, while some .458 SOCOM AR15s may use 5/8x32 or 5/8x24 threads.

Here is a list of the most common thread pitches by caliber for AR15 barrels:

This list is based on the normal thread pitches per caliber, but some manufacturers may use different thread pitches for their barrels. You should always check with your manufacturer if you can.

How to Identify Thread Pitch on an AR15 Barrel

If you are not sure what thread pitch is on your AR15 barrel, there are a few ways to tell:

Measure it with a caliper or a ruler. You can use a caliper or a ruler to measure the diameter and the distance between the threads on your barrel. For example, if your barrel has a diameter of half an inch and the distance between two threads is 0.028 inches, then your thread pitch is 1/2x28.

Compare it with another barrel or muzzle device. You can use another barrel or muzzle device that has a known thread pitch to compare with your barrel. For example, if you have a flash hider that is 1/2x28 and it fits your barrel snugly, then your thread pitch is also 1/2x28. If it does not fit or gets stuck after a few turns, then your thread pitch is different.

Use a thread pitch gauge. You can use a thread pitch gauge to determine the thread pitch on your barrel. A thread pitch gauge is a tool that has different blades with different thread pitches marked on them. You can insert the blade that matches your barrel's threads and read the thread pitch on the blade.

How to Choose the Right Muzzle Device for Your AR15 Barrel

Once you know what thread pitch is on your AR15 barrel, you can choose the right muzzle device for your rifle. Muzzle devices are accessories that attach to the end of the barrel and affect the performance and appearance of your rifle. There are four main types of muzzle devices:

Flash hiders. Flash hiders are designed to reduce or eliminate the flash of the muzzle blast, making it harder for enemies to spot you in low-light conditions. Flash hiders are usually open-ended and do not affect the recoil or accuracy of your rifle. Flash hiders are compatible with most thread pitches and calibers, as long as the bore diameter is large enough to allow the bullet to pass through.

Muzzle brakes. Muzzle brakes are designed to reduce the recoil and muzzle rise of your rifle, making it easier to control and shoot faster. Muzzle brakes are usually closed-ended and have ports or vents that redirect the gas sideways or backwards, creating a counter-force that reduces the recoil. Muzzle brakes are not compatible with all thread pitches and calibers, as they need to match the bore diameter and bullet weight of your rifle. Using a muzzle brake with a smaller bore diameter or a lighter bullet can cause damage to your rifle or injury to yourself.

Compensators. Compensators are designed to reduce the muzzle rise and drift of your rifle, making it more accurate and consistent. Compensators are usually closed-ended and have ports or vents that redirect the gas upwards or sideways, creating a counter-force that reduces the muzzle movement. Compensators are not compatible with all thread pitches and calibers, as they need to match the bore diameter and bullet weight of your rifle. Using a compensator with a smaller bore diameter or a lighter bullet can cause damage to your rifle or injury to yourself.

Suppressors. Suppressors are designed to reduce the noise and flash of your rifle, making it quieter and stealthier. Suppressors are usually cylindrical devices that attach to the end of the barrel and have baffles or chambers that trap and slow down the gas, reducing the sound pressure and temperature. Suppressors are not compatible with all thread pitches and calibers, as they need to match the bore diameter and bullet weight of your rifle. Using a suppressor with a smaller bore diameter or a lighter bullet can cause damage to your rifle or injury to yourself.

When choosing a muzzle device for your AR15 barrel, you need to consider the following factors:

Thread pitch compatibility. You need to choose a muzzle device that has the same thread pitch as your barrel, otherwise it will not fit or function properly. You can use adapters or spacers to convert different thread pitches, but they may affect the alignment or performance of your muzzle device.

Bore diameter compatibility. You need to choose a muzzle device that has a bore diameter that is equal to or larger than your bullet caliber, otherwise it will obstruct or damage your barrel or muzzle device. You can use washers or shims to adjust the bore diameter, but they may affect the alignment or performance of your muzzle device.

Bullet weight compatibility. You need to choose a muzzle device that is designed for the bullet weight that you use, otherwise it will not work as intended or cause excessive wear or stress on your barrel or muzzle device. You can use different loads or powders to adjust the bullet weight, but they may affect the accuracy or reliability of your rifle.

Performance goals. You need to choose a muzzle device that suits your performance goals, whether you want to reduce flash, recoil, muzzle rise, drift, noise, or a combination of these factors. You also need to consider the trade-offs of each type of muzzle device, such as increased blast, weight, length, cost, legality, etc.

Conclusion

AR15 thread pitch is an important factor that affects the compatibility and performance of muzzle devices on your rifle. You need to know what thread pitch is on your barrel and how to identify it using various methods. You also need to know how to choose the right muzzle device for your barrel based on thread pitch compatibility, bore diameter compatibility, bullet weight compatibility, and performance goals.

We hope this article has helped you understand AR15 thread pitch better and how it relates to muzzle devices. If you have any questions or comments, please feel free to contact us.