1/2–28 vs. 5/8–24.
These are two common muzzle-device thread pitches, and Plan B offers flash comps and brake comps in both. The correct choice is determined by the exact barrel—not by appearance, firearm category or a general assumption about caliber.
What the numbers mean.
In an inch-based thread designation, the first number is the nominal major diameter and the second is the number of threads per inch. A 1/2–28 thread is nominally one-half inch in diameter with 28 threads per inch. A 5/8–24 thread is nominally five-eighths inch in diameter with 24 threads per inch. The Plan B products listed here use right-hand versions of both pitches.
| Thread pitch | Plan B flash comp | Plan B brake comp | Brake caliber rating |
|---|---|---|---|
| 1/2–28 RH | Flash Comp 1/2–28 | Brake Comp 1/2–28 | .224 or smaller |
| 5/8–24 RH | Flash Comp 5/8–24 | Brake Comp 5/8–24 | .308 or smaller |
Why thread pitch is only the first check.
Caliber and bore
A matching thread can still be unsafe if the projectile is larger than the muzzle device or suppressor bore allows.
Shoulder and seating
The device must seat against the correct mounting surface without interference, bottoming or an unsuitable shoulder.
Suppressor system
For suppressed use, verify the Plan B mount, HUB adapter, depth, alignment and every operating limit too.
Thread pitch is a necessary mechanical match, not a complete compatibility determination. A different barrel profile, shoulder arrangement, thread relief or manufacturer restriction can change the answer even when the nominal pitch is the same.
A practical verification sequence.
- Read the barrel maker’s current specifications.
- Confirm thread diameter, pitch and direction.
- Confirm the muzzle device’s caliber or bore rating.
- Inspect the shoulder and thread relief requirements.
- Choose flash comp or brake comp behavior.
- Confirm timing hardware and installation instructions.
- For suppressed use, check mount and internal depth.
- Verify alignment before firing through a suppressor.
Frequently asked questions.
Can I identify muzzle threads by caliber alone?
No. Caliber may suggest a commonly used pitch, but it does not identify the exact barrel thread. Confirm it from the barrel manufacturer or qualified measurement.
Are the Plan B threads right-hand?
Yes. The listed Plan B 1/2–28 and 5/8–24 products specify right-hand threads.
Do both thread pitches work with a Plan B suppressor mount?
The muzzle-device side can share Plan B mounting geometry, but the barrel thread, bore, adapter, suppressor depth, alignment and manufacturer approval all require separate verification.