a second set of wheels were fitted. Extended specification Gun Length: weight: 9 cwt Rifling: 18 grooves (Mks I, II, IV) Twist: 1 in 30 (Mks I, II, IV) Barrel Life: 12,000 to 15,000 rounds Carriage weight: 24 cwt (Mk V 27 cwt) Width: recoil: 41 inches fixed (carriage Mk I, II); 26 – 48 inches variable (carriage Mk IV, Mk V) Elevation: -5° to +16° (carriage Mk I & II with pole trail), +30° (carriage Mk III box trail), +37° (carriage Mk IV box trail & Mk V split trail) Traverse: 4.5° left and right (Carriage Mk I – IV); 25° left and right (carriage Mk V) Gunshield: proof against shrapnel and rifle fire (500 yds) Limber Capacity: 24 shells weight: 14 cwt First World War 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 By 1914, this cordite had been replaced by Cordite MD.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 the First World War 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 Krupp 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 First World War time fuzes), meaning that it burnt 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