Interrupted screw

The screw can thus be smoothly inserted all the way into the receptacle, after which as little as one-eighth of a turn can engage the two sets of threads securely, sealing the joint.

[2] In the artillery application, the screw is set into the breechblock and mated with a partially threaded hole at the rear of the weapon's chamber.

American engraver Benjamin Chambers, Sr.[3] received a patent[4] in 1849 for a wrought iron built-up gun "dissected screw breech" with "sectional screws" "cut therein for the purpose of speedily opening the breech for swabbing, depositing the load, and readily closing it again when the gun is to be discharged".

His gun was built and tested with metallic cartridges, center-primed with a percussion cap, because the US Navy was initially interested, and chief of the Bureau of Ordnance Charles Morris recommended more developments, but the system was too expensive for the time and cheaper Dahlgren guns were adopted instead.

Interrupted screws are occasionally seen in loose gunpowder rifles, as this mechanism was historically one of the few practical ways to achieve a gas-proof seal with a breech-loading firearm that does not employ metallic cartridges.