1/2–28 vs. 5/8–24.
These are two common muzzle-device and direct-thread attachment pitches. Plan B offers flash comps, brake comps and Direct-Thread HUB Adapters in both, plus corresponding 1/2-inch and 5/8-inch ID peel washers for compatible timed installations.
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 flash comps and brake comps listed here specify right-hand versions of both pitches.
| Barrel thread | Flash comp | Brake comp | Direct-thread HUB adapter | Timing washer |
|---|---|---|---|---|
| 1/2–28 RH | Flash Comp 1/2–28 | Brake Comp 1/2–28 | 1/2–28 Direct Thread | 1/2-inch ID · 6 pack |
| 5/8–24 RH | Flash Comp 5/8–24 | Brake Comp 5/8–24 | 5/8–24 Direct Thread | 5/8-inch ID · 4 pack |
Peel washers are listed by inside diameter, not by thread pitch. They provide small thickness adjustments for indexing a compatible muzzle device; they do not determine or change the barrel thread.
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 component must seat against the correct mounting surface without interference, bottoming or an unsuitable shoulder.
Suppressor system
For suppressed use, choose a supported Plan B or direct-thread path, then verify adapter fit, depth, alignment and every operating limit.
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 or suppressor system’s caliber and bore rating.
- Inspect the shoulder and thread relief requirements.
- Choose a supported Plan B or direct-thread mounting path.
- If using a timed muzzle device, confirm washer dimensions and installation instructions.
- For suppressed use, check adapter fit 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 muzzle-device threads right-hand?
Yes. The listed Plan B flash comps and brake comps specify right-hand 1/2–28 or 5/8–24 threads. Confirm the specifications on the exact product page before ordering.
Can one Direct-Thread HUB Adapter fit both pitches?
No. The 1/2–28 and 5/8–24 adapters are separate products. Choose only the model that matches the barrel and is supported by the suppressor manufacturer.
Does a peel washer change thread compatibility?
No. A peel washer adjusts spacing for indexing a compatible muzzle device. It does not make one thread pitch fit another.
Do both muzzle-device 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.