Pistol Barrels

Barrel Threading

Barrel threading is a machining process that cuts helical grooves (threads) into the muzzle end of a firearm barrel, allowing the barrel to accept threaded muzzle devices such as muzzle brakes, compensators, flash hiders, and suppressors (silencers). A gunsmith or machinist uses a lathe to cut threads to a specific diameter and pitch — measured in threads per inch (TPI) — that match the muzzle device's internal threads. The 2 most common barrel thread pitches are 1/2x28 TPI for 5.56 NATO/.223 Remington and 9 mm calibers, and 5/8x24 TPI for .308 Winchester/7.62 NATO and 6.5 Creedmoor calibers. This guide covers what a threaded barrel is, the threading process, common thread sizes for rifles and pistols, threaded vs non-threaded barrels, thread adapters, Quick-Detach (QD) mounts, and barrel threading costs.

What Is a Threaded Barrel?

A threaded barrel is a firearm barrel with external helical threads machined into the muzzle end that accept screw-on muzzle devices. The threads are cut concentric to the bore, and a thread protector (a threaded cap) covers the exposed threads when no muzzle device is installed. Threaded barrels come in 2 forms: factory-threaded barrels that ship with threads from the manufacturer, and aftermarket-threaded barrels that a gunsmith machines from a non-threaded barrel.

What Does a Threaded Barrel Do?

A threaded barrel allows 4 types of muzzle devices to attach securely to the barrel: muzzle brakes for recoil reduction, compensators for muzzle rise control, flash hiders for flash suppression, and suppressors for sound reduction. The threads create a mechanical lock between the barrel and the muzzle device, and a crush washer, jam nut, or shim kit prevents the device from loosening under recoil.

How Are Gun Barrels Threaded?

To thread a gun barrel, a gunsmith mounts the barrel in a lathe, centers the bore using a bore-indicating rod, and cuts threads with a single-point threading tool or a thread-cutting die. The barrel threading process follows 6 steps:

1. Remove the barrel from the firearm action and strip all accessories
2. Mount the barrel in a lathe chuck and align the bore axis with the lathe spindle using a bore indicator accurate to 0.001 inches (0.025 mm)
3. Turn the muzzle end to the correct major diameter for the thread specification — 0.500 inches (12.7 mm) for 1/2x28 TPI or 0.625 inches (15.875 mm) for 5/8x24 TPI
4. Cut a thread relief (undercut) at the base of the threaded section to allow the muzzle device to seat flush against the barrel shoulder
5. Cut the threads using a single-point tool at the correct pitch, making multiple passes at 0.002 to 0.005 inches (0.05 to 0.13 mm) depth per pass
6. Check the threads with a thread ring gauge to verify Class 2A fit tolerance, then crown the muzzle with an 11-degree target crown or a recessed crown

Can a Barrel Be Threaded at Home?

Yes, a barrel can be threaded at home with a barrel threading kit that includes a threading die, a die starter, an alignment guide, and a thread pitch gauge, priced at $150 to $400. Home barrel threading requires the die to align perfectly with the bore axis, and misalignment of more than 0.003 inches (0.076 mm) produces threads that are not concentric with the bore. Non-concentric threads cause the muzzle device to sit off-center, which deflects gases unevenly and shifts the point of impact.

Where to Get a Barrel Threaded

A barrel threading service is available at local gunsmiths, machine shops with firearms experience, and online gunsmithing services. Barrel threading costs $75 to $200 depending on the caliber, thread pitch, and barrel material (stainless steel vs chrome-moly steel). The turnaround time for professional barrel threading is 1 to 4 weeks. Request Class 2A thread tolerance and a thread gauge check before accepting the finished barrel.

Common Barrel Thread Sizes for Rifles

Rifle barrels use 5 standard thread pitches based on caliber:

5.56 NATO / .223 Remington Barrel Thread Size

The standard thread pitch for 5.56 NATO and .223 Remington barrels is 1/2x28 TPI with a major diameter of 0.500 inches (12.7 mm). All AR-15 rifles, including the Colt AR-15, HK416, HK MR223, and HK MR556, use 1/2x28 threads from the factory. The 1/2x28 pitch is the most common thread pitch in the United States firearms market.

6.5 Creedmoor Barrel Thread Size

The standard thread pitch for 6.5 Creedmoor barrels is 5/8x24 TPI with a major diameter of 0.625 inches (15.875 mm). The 5/8x24 pitch provides a larger thread engagement area than 1/2x28, supporting the heavier muzzle devices and higher bolt thrust of the 6.5 Creedmoor cartridge.

.308 Winchester / 7.62 NATO Barrel Thread Size

The standard thread pitch for .308 Winchester and 7.62 NATO barrels is 5/8x24 TPI, the same pitch used on 6.5 Creedmoor barrels. AR-10 rifles, bolt-action rifles such as the Remington 700, and semi-automatic rifles in .308 use 5/8x24 threads.

.338 Lapua Magnum Barrel Thread Size

The standard thread pitch for .338 Lapua Magnum barrels is 5/8x32 TPI or 3/4x24 TPI depending on the barrel manufacturer. The finer 5/8x32 pitch provides more thread engagement per inch than 5/8x24, supporting the 80,000+ psi (5,516+ bar) chamber pressure of the .338 Lapua Magnum cartridge.

.50 BMG Barrel Thread Size

The standard thread pitch for .50 BMG (Browning Machine Gun) barrels is 3/4x24 TPI or 1x14 TPI depending on the rifle model. The Barrett M82 uses a proprietary muzzle brake mount, and custom .50 BMG bolt-action rifles from Serbu and McMillan use 3/4x24 or 1x14 threads.

Common Barrel Thread Sizes for Pistols

Pistol barrels use 4 standard thread pitches based on caliber:

9 mm Barrel Thread Size

The standard thread pitch for 9 mm pistol barrels is 1/2x28 TPI in the United States and M13.5x1 Left Hand (LH) in Europe. Factory-threaded 9 mm barrels are available from Glock, SIG Sauer, Smith & Wesson, and Springfield Armory.

.45 ACP Barrel Thread Size

The standard thread pitch for .45 ACP (Automatic Colt Pistol) barrels is .578x28 TPI with a major diameter of 0.578 inches (14.68 mm). The larger diameter accommodates the .452 inch (11.48 mm) bullet diameter of the .45 ACP cartridge.

.40 S&W Barrel Thread Size

The standard thread pitch for .40 S&W (Smith & Wesson) barrels is 9/16x24 TPI with a major diameter of 0.5625 inches (14.29 mm).

.22 LR Barrel Thread Size

The standard thread pitch for .22 LR (Long Rifle) rimfire barrels is 1/2x28 TPI, the same pitch used on 5.56 NATO and 9 mm barrels. The shared thread pitch allows .22 LR shooters to use the same suppressors and muzzle devices designed for centerfire 5.56 and 9 mm barrels.

Threaded vs Non-Threaded Barrels

A threaded barrel provides 4 benefits over a non-threaded barrel: muzzle device compatibility, suppressor mounting, recoil management, and resale value. A non-threaded barrel cannot accept a muzzle brake, compensator, flash hider, or suppressor without first being threaded by a gunsmith. Threaded barrels do not affect accuracy when the threads are cut concentric to the bore.

Do You Need a Threaded Barrel for a Suppressor?

Yes, a threaded barrel is required for direct-thread suppressor mounting, and a threaded muzzle device is required for QD suppressor mounting. Direct-thread suppressors screw onto the barrel threads, and QD suppressors lock onto a compatible muzzle device (muzzle brake or flash hider) that is already threaded onto the barrel.

Thread Adapters and QD Mounts

Thread adapters convert one barrel thread pitch to another, allowing a muzzle device with a different thread pitch to mount on the barrel. A 1/2x28-to-5/8x24 thread adapter allows a .308-caliber muzzle brake to mount on a 5.56-caliber barrel. QD mounts use a locking mechanism — ratchet, cam, or taper — that attaches a suppressor to a muzzle device in under 3 seconds. Boosters (also called Nielsen devices or pistons) are spring-loaded adapters required for mounting a suppressor on a tilting-barrel semi-automatic pistol, because the added weight of the suppressor prevents the barrel from unlocking without the booster's spring assistance. Shooters who need muzzle brakes for recoil reduction or flash hiders and compensators for muzzle control can compare thread-compatible options across calibers.

Do Threaded Barrels Affect Accuracy?

No, threaded barrels do not affect accuracy when the threads are cut concentric to the bore within 0.001 to 0.002 inches (0.025 to 0.05 mm) Total Indicated Runout (TIR). The threading process removes metal from the exterior of the barrel at the muzzle, not from the bore, so the rifling and crown remain unchanged. A properly crowned muzzle — cut at 11 degrees or recessed — ensures gas exits the barrel symmetrically around the bullet, and concentricity of the muzzle device to the bore prevents uneven gas deflection.