Barrel threads

Furthermore, recoil-operated firearm designs have moving barrels (e.g. most pistols or the Barrett M82 rifle).

[citation needed] Many older rifles from the first half of the 20th century use a thread pitch around 2 mm (12.7 TPI), while many modern rifle use thread pitches around 1.5 mm (16.93 TPI).

[3] If the barrel, receiver and bolt are not fitted properly, severe and potential fatal problems can arise due to faulty headspace, e.g. cartridge overpressure and case rupture.

Threaded barrels are often mounted to the receiver with a lot of torque, and will therefore generally require tools for assembly and disassembly, such as a suitable action wrench and a vise.

The applicable thread is limited to a certain degree by the bullet caliber and barrel diameter.

Some common barrel threads are listed below:[67][68][69][70] Some accessories, notably suppressors and concussion reduction devices (CRDs), attach via a muzzle device such as a flash hider, compensator, thread protector or sleeve.