Ordnance QF 18 Pounder - World War I Ammunition

World War I Ammunition

18-pounder ammunition was a fixed round (i.e. the shell and brass cartridge case were loaded as a single unit, much like a large rifle cartridge), and fitted with a nose fuze. The normal service round was "Full Charge", a "Reduced Charge" round was available for training. Double base propellant (nitroglycerine and nitrocellulose) was used, Cordite Mark 1 was the standard propellant when the gun was first introduced into service. By 1914 this cordite had been replaced by Cordite MD. During World War I this was replaced by a revised formulation that was easier to produce called Cordite RDB.

Until September 1914 the only 18-pounder issued shell was shrapnel, fitted with a No. 80 "Time & Percussion" fuze (based on a Krupps design). The timer was set to open the shell and fire the bullets forward before it hit the ground. No 80 Fuze was an igniferous type of time fuze (as were most World War I time fuzes), meaning it burnt a gunpowder at a known rate to give a time from firing to fuze functioning. The shell did not burst, but projected spherical lead-antimony bullets forward in a cone, these bullets were effective up to 300 yards from the burst. 18-pounder carried 374 of the 41/pound size bullets. The fuze was designed to function as close as 50 yards from the muzzle if required, in order to eliminate the need for case shot. Observing shrapnel bursts was difficult, and after many experiments gunpowder pellets were added to the tube between the fuze and the gunpowder ejecting charge in the base of the shell in order to emit a puff of smoke, this had the added advantage of widening the cone of the bullet spread.

A star shell with a time fuze (No 25) had been developed and small stocks were held before the war but it was not routine issue.

Pre-war experiments with 18-pounder HE shells had been inconclusive in terms of their benefits. However, the first month of World War I showed that they were worth having and the first HE rounds arrived in September 1914. This was a different shape to the existing shrapnel shell so a new Mark 2 shrapnel shell was introduced to ensure ballistic compatibility. The original shrapnel shells had a relatively blunt ogive - 1.5 circular radius head (crh), the newer ones were 2 crh.

In 1914 the standard HE used by UK artillery was Lyddite, a formulation based on picric acid, this was a powerful explosive but expensive. TNT was introduced, but this too was expensive, particularly in its pure form required for shells so eventually Amatol was adopted. This was a mixture of ammonium nitrate and lower quality TNT, various proportions were used but eventually 80% ammonium nitrate and 20% TNT became standard. The parallel inside walls of the shell made it suitable for filling using pre-formed blocks of explosive as well as pouring.

Other types of shell were also introduced, although not as extensively as they were for howitzers and heavier guns. White phosphorus smoke shells became available in small quantities in 1916, and in 1918 chemical and incendiary shells were provided. The latter were a shrapnel type shell using thermite pellets, although a black powder incendiary shell for AA use against Zeppelins was introduced in 1916.