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The Ordnance QF 25-pounder, or more simply 25-pounder or 25-pdr, was the major British field gun and howitzer during World War II. It was introduced into service just before the war started, combining high-angle and direct-fire, relatively high rates of fire, and a reasonably lethal shell in a highly mobile piece. It remained the British Army's primary artillery field piece well into the 1960s, with smaller numbers serving in training units until the 1980s. Many Commonwealth of Nations countries used theirs in active or reserve service until about the 1970s and ammunition for the weapon is currently being produced by Pakistan Ordnance Factories. ==Design== The design was the result of extended studies looking to replace the 18-pounder ( bore) field gun and the 4.5-inch howitzer (114.3 mm bore), which had been the main field artillery equipments during the First World War. The basic idea was to build one weapon with the high velocity of the 18-pounder and the variable propelling charges of the howitzer, firing a shell about half way between the two in size, around of about . Development during the inter-war period was severely hampered by a lack of money and it was eventually decided to build a "new" design from existing 18-pounders by converting barrels but designing a new barrel and carriage for production when funds were available. The result was a weapon firing a shell weighing . It was mounted on late model 18-pounder carriages. One of these used a circular firing platform and this was adopted for the new guns. The firing platform was attached to the gun and when lowered the gun was pulled onto it. This platform transferred most of the recoil forces to the ground, instead of using the spade at the end of the trail, making the gun very stable when firing. It also provided a flat smooth surface for the carriage to rotate on using the road wheels, this enabled the gunners to traverse the carriage quickly in any direction. Unlike the 18-pounder, the 25-pounder used howitzer-type variable-charge ammunition. The 25-pounder was separate-loading; the shell was loaded and rammed, then the cartridge in its brass case was loaded and the breech closed. In British terminology the 25-pounder was called "quick firing" (QF), originally because the cartridge case provided rapid loading compared with bag charges, and was automatically released when the breech was opened. The use of separate shell and cartridge allowed the charge to be changed for different ranges. For the Mk 1 Ordnance on an 18-pounder carriage there were three "charges", charges one, two and three, all of which could be used in the common cartridge design. The Mk 2 Ordnance on Mk 1 carriage added a "super" charge in a different cartridge. In 1943 a separately bagged "increment" charge was added; used with the Super it provided higher velocity for anti-tank use. The introduction of the increment to super was only possible following the addition of the muzzle-brake in the previous year. Subsequently another type of increment was introduced to be added to charges one and two to provide additional combinations for use in high angle fire. However, this fire required a dial sight adaptor, removal of the platform and some excavation of the ground. In common with all British guns of the period the indirect fire sight was "calibrating". This meant that the range, not elevation angle, was set on the sight. The sight compensated for the difference in the gun's muzzle velocities from standard. The gun was also fitted with a direct-fire telescope for use with armour-piercing shot. It also used "one-man laying" in accordance with normal British practice. An important part of the gun was the ammunition trailer ("trailer, artillery, No 27"). The gun was hooked to it and the trailer hooked to the tractor for towing. The gun did not need a limber〔Limbers were necessary for horse-drawn artillery.〕 and could be hooked directly to a tractor. The trailer provided the brakes as only a hand-brake was fitted to the gun carriage. The trailer carried ammunition; thirty-two rounds in trays (two rounds per tray) in the trailer protected by two doors. Ammunition was also carried in the gun tractor with the detachment and various gun stores. Some stores, such as sights, were carried cased on the gun. Each section (two guns) had a third tractor that carried ammunition and towed two ammunition trailers. The gun detachment comprised the following: No 1 – detachment commander (a sergeant) No 2 – operated the breech and rammed the shell No 3 – layer No 4 – loader No 5 – ammunition No 6 – ammunition, normally the 'coverer' – second in command and responsible for ammunition preparation and operating the fuze indicator The official 'reduced detachment' was four men. Many different companies manufactured the guns and component parts in the UK. Vickers Armstrong in Scotswood, Baker Perkins in Peterborough and Weirs in Glasgow were some of the most significant. The various Royal Ordnance factories produced most of the ordnance components. In Canada, Sorel Industries built complete guns and provided the ordnance for fitting to the Sexton. Australia also built complete guns, choosing to weld the carriages rather than rivet, as was the practice in the UK and Canada. In all, over 13,000 were made worldwide. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ordnance QF 25-pounder」の詳細全文を読む スポンサード リンク
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