The double cylinder, Nos. 8 and No. 9 hand grenades, also known as the "jam tins", are a type of improvised explosive device used by the British and Commonwealth forces, notably the Australian and New Zealand Army Corps (ANZAC) in World War I (1914–1918). The jam tin, or bully beef tin, was one of many grenades designed by ANZACs in the early part of the First World War in response to a lack of equipment suited to trench warfare.
Background
In late 1914, once the Germans superiority in grenades and trench mortars became apparent, the British appointed Colonel Louis Jackson, Assistant Director of Fortifications and Works to develop British equivalents, including the Jam tin in collaboration with the Roburite & Ammonal Company.
While some accounts including James Dunn's The War Infantry Knew (1938) suggests that improvised Jam tins were used in France as early as December 1914, Jackson's own account claimed that the No. 8 and No. 9 grenades were introduced first while the improvised versions appeared later. According to Saunders, the Bengal Sappers and Miners used their pre-war experience to build improvised grenades including the Jam tin grenade, which was later standardized for mass production as the Nos 8 and 9 until the Mills bomb could be produced in sufficient numbers for the troops.
Design
The grenade was an inner can of explosive with an outer can of metal fragments or bearing balls. The heavier The Jam tin grenade was always in short supply however, and during the fighting against the Turks they were constantly at risk of being bombed out of their trenches, sometimes being forced to throwing Turkish grenades back before they detonated or make use of other types of improvised grenades.
During the Siege of Kut in Mesopotamia (December 1915–April 1916), the Royal Engineers in General Townshend's force improvised jam pot mortar shells to be used with improvised mortars devised from the cylinders of a Gnome rotary engine (credit to Capt. R.E. Stace, RE). The engine came from a Martinsyde S.1 scout plane, likely damaged or otherwise unable to evacuate.
Improvised explosive devices of this type were also used to a limited extent during World War II (1939–1945): SOE and OSS agents, before being parachuted behind enemy lines, were trained to construct various types of improvised ordnances, including tin can grenades; instructions regarding the construction of "Jam-tin Grenades" were also included in the training for the British Home Guard.
thumb|Tin Can Grenade.
An improvised explosive device designated "Tin Can Grenade" remained in the arsenal of the United States Army Special Forces at least until the 1960s.