What Thread Pitch Does My AR-15 Muzzle Use for Muzzle Devices?
Standard AR-15 barrels in 5.56 NATO and .223 Remington use 1/2 x 28 TPI (threads per inch) muzzle threads. AR-10 barrels in .308 Winchester and 7.62 NATO use 5/8 x 24 TPI. Other calibers vary, always verify your barrel's thread pitch before purchasing a muzzle device.
What This Means for Your Build
Installing a muzzle device with the wrong thread pitch can damage the barrel threads, and a device that does not seat properly against the barrel shoulder is a safety hazard. Cross-threading a muzzle device can be expensive to fix, potentially requiring the barrel to be re-threaded or replaced.
The Detail
Common AR-platform muzzle thread pitches by caliber:
1/2 x 28 TPI:
- 5.56 NATO / .223 Remington / .223 Wylde
- 300 Blackout
- .22 LR AR conversions
- .224 Valkyrie
- 9mm PCC (some models)
- This is the most common AR-15 thread pitch
5/8 x 24 TPI:
- .308 Winchester / 7.62 NATO (AR-10)
- 6.5 Creedmoor (AR-10)
- 6.5 Grendel (some manufacturers, others use 1/2 x 28)
- .350 Legend (some manufacturers)
- .450 Bushmaster
- .458 SOCOM
Other thread pitches:
- 9mm PCC: 1/2 x 28 or 1/2 x 36 depending on manufacturer
- .50 Beowulf: 49/64 x 20 TPI
Muzzle device types:
- Flash hiders: Reduce visible flash signature (A2 birdcage is standard mil-spec)
- Muzzle brakes: Reduce felt recoil by redirecting gas (increase blast and noise to sides)
- Compensators: Reduce muzzle rise (similar to brakes but focused on vertical control)
- Suppressor mounts: Thread-on or quick-detach mounts that serve as the suppressor mounting interface
Suppressor compatibility:
If you plan to run a suppressor, your muzzle device must be compatible with your specific suppressor's mounting system. Common systems include:
- SilencerCo ASR
- Dead Air KeyMo
- SureFire SOCOM
- Q Plan B / Cherry Bomb
- Direct thread (simplest but slowest to attach/detach)
Build Impact
Always verify thread pitch before ordering a muzzle device. When installing, use a crush washer (for non-timed devices) or shims (for precision timing). Tighten to manufacturer specifications. For pin-and-weld applications (making a 14.5-inch barrel legal 16-inch OAL), ensure your muzzle device adds enough length and have it professionally welded. Apply rocksett or similar high-temperature thread locker if not using a crush washer.