List of British Ordnance Terms - HE

HE

See also: Shell (projectile)#High-explosive (HE)

"HE" in British terminology initially designated only shells filled with modern "high explosive" such as Trotyl (the British term for TNT), which was being introduced when World War I began, and Amatol from 1915. It contrasted with Common Shell, which were filled with older explosives such as gunpowder, and Common Lyddite, the earlier British high explosive shell. Britain also used Tetryl before World War I under the designation "Composition Exploding" (C.E.).

The HE shell filling was detonated by a fuze, usually augmented by a "gaine" to ensure complete ignition, causing the thick steel shell case to shatter into large and small fragments at great velocity in all directions.

Britain first used pure TNT for land warfare shells from late 1914, but this proved expensive and difficult to manufacture in the necessary large quantities, and was also inefficient as much energy was output as heavy black smoke. Amatol, a mixture of cheap Ammonium Nitrate and TNT (initially "40/60" : 40% ammonium nitrate and 60% TNT for land shells and 80/20 from 1917) proved 27% more powerful than pure TNT and was soon adopted as the preferred HE filling in World War I. TNT and Amatol were approximately 20% less sensitive to shock and hence safer than Lyddite, and Amatol 80/20 cost only 7d per pound to produce in 1917 compared to 1s 11d for lyddite and 1s 3d for TNT.

Britain was slow to move from 40/60 Amatol to the preferred 80/20 mixture during World War I, due to manufacturing difficulties. The preferred method for filling explosive shells was by pouring the molten mixture through the fuze hole in the shell nose or base. This was well suited to Lyddite filling, but it was found that Amatol with more than 40% Ammonium Nitrate did not pour well. Hence it was not simply a case of switching existing filling machinery from Lyddite to Amatol. Dry filling with Amatol 80/20 in block form and by pressing was used but was not considered to be a success. By the end of World War I the process for pouring 80/20 Amatol as a shell filling for land warfare shells had finally been perfected and was in large–scale production.

The Royal Navy resisted switching from Lyddite to Amatol for its shells because it considered Amatol was too hygroscopic (water-absorbing) to be suitable for use at sea, and instead used pure TNT as its high-explosive replacement for Lyddite. After World War I, remaining stocks of Lyddite-filled naval shells were redesignated "H.E. Shell Filled Lyddite", and henceforth the term H.E. encompassed all Lyddite, TNT and subsequent high-explosive shell types. From 1919 into the 1930s a less sensitive and safer version of Lyddite named Shellite, consisting of 70% Lyddite and 30% dinitrophenol was used in naval AP shells.

Amatol continued in field use to 1945 when it began to be replaced by a 60/40 mixture of RDX and TNT.

HE shells were typically painted yellow in British service in World War I, with a red ring below the nose to indicate the shell was filled and a green ring round the body to indicate filling with TNT or Amatol. In World War II they were typically painted olive green.