# Will a 1/2x28 muzzle device fit a 5/8x24 barrel?

**Verdict: No**

No. The two thread pitches are different diameters and different pitches — the device will not start, and forcing it damages the barrel threads.

These are not near-misses in either direction. 1/2x28 is a half-inch major diameter at 28 threads per inch; 5/8x24 is five-eighths at 24 — an eighth of an inch larger across, or 25 per cent. A 1/2x28 device will not pass over a 5/8x24 barrel at all. In the other direction a 5/8x24 device does not thread on loosely either: its threads never reach a 1/2x28 barrel, so it slides straight over and falls off. Nothing about either combination can be made to hold by tightening it.

- **1/2x28** — Standard on .223 / 5.56 AR-15 barrels
- **5/8x24** — Standard on .30-calibre barrels — .308, and .300 Blackout
- **Thread adapters** — Sold for some combinations — check the specific pair rather than assume

Thread pitch follows bore size by convention rather than by platform, which is where people are caught out. A .300 Blackout upper is an AR-15 upper in every other respect and is normally threaded 5/8x24, because the convention tracks the .30-calibre bore rather than the rifle it sits in.

> **Caution:** A muzzle device has to seat squarely against the barrel shoulder. One that does not — because it is the wrong pitch, or because it was forced — is unsupported at the moment a bullet passes through it. Do not start a device that does not turn freely by hand.

## Sources

- [Common barrel thread patterns — 1/2x28 and 5/8x24 by calibre](https://www.silencercentral.com/blog/silencer-common-barrel-thread-patterns/)
- [Barrel threads — muzzle thread standards](https://en.wikipedia.org/wiki/Barrel_threads)

## More on barrels and muzzle devices

- [Are all AR-15 barrels threaded 1/2x28?](https://www.tactgpt.app/answers/are-all-ar15-barrels-threaded-half-inch-28.md)

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Last checked 2026-09-03. TactGPT can make mistakes. Always check important info for accuracy. The information it provides is intended for educational purposes only. It does not give legal advice; verify any laws cited. Always follow all applicable laws and safety guidelines.

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