Threaded Barrel
A barrel with threads cut at the muzzle for attaching a suppressor or muzzle device.
A threaded barrel has machine threads on its outside diameter just behind the muzzle, sized to fit a suppressor, compensator, muzzle brake, or flash hider. Common pistol thread pitches are 1/2-28 (for 9mm) and 1/2-36 (for .45 ACP); rifle pitches vary by caliber. Threaded barrels are restricted in some jurisdictions even when the attachments themselves aren’t.