Figure415 Stepped-thread interrupted-screw breech block

An Asbury Mechanism opens and closes the breech of heavy artillery for reloading with a projectile and bags of

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...

. It was widely used for

naval artillery Naval artillery is artillery mounted on a warship, originally used only for naval warfare and then subsequently used for more specialized roles in surface warfare such as naval gunfire support (NGFS) and anti-aircraft warfare (AAW) engagements. ...

of the

world war A world war is an international War, conflict that involves most or all of the world's major powers. Conventionally, the term is reserved for two major international conflicts that occurred during the first half of the 20th century, World War I ...

s and similar

coastal artillery Coastal artillery is the branch of the armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications. From the Middle Ages until World War II, coastal artillery and naval artillery in the form of ...

and

railway gun A railway gun, also called a railroad gun, is a large artillery piece, often surplus naval artillery, mounted on, transported by, and fired from a specially designed railroad car, railway wagon. Many countries have built railway guns, but the ...

s. The device was invented at the

Washington Navy Yard The Washington Navy Yard (WNY) is a ceremonial and administrative center for the United States Navy, located in the federal national capital city of Washington, D.C. (federal District of Columbia). It is the oldest shore establishment / base of ...

in 1916 by draftsman Dorsey Frost Asbury. It is sometimes called a Smith-Asbury mechanism by the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

in recognition of Asbury's supervisor, Lieutenant Commander George Leonard Smith, USN. Large caliber breech-loading artillery became practical with French development of the obturator by Charles Ragon de Bange in 1872; and speed of reloading was improved by adaptation of the

interrupted screw file:Breech 122m10 hameenlinna 2.jpg, Breech from Russian 122 mm M1910 howitzer, modified and combined with 105 mm H37 howitzer barrel An interrupted screw or interrupted thread is a mechanical device typically used in the Breech-loadi ...

breech plug, which was later further improved by Axel Welin in 1890 as the Welin breech block and adopted by the Swedish. Asbury used gearing to fully open a Welin breech by linking the unscrewing, withdrawing and swinging clear movements into one continuous action.

Sources

* {{US Patent, 1185964A Artillery components