Ordnance QF 25-pounder
The Ordnance QF 25-pounder, or more simply 25-pounder or 25-pdr, with a calibre of 3.45 inches, was a piece of field artillery used by British and Commonwealth forces in the Second World War. Durable, easy to operate and versatile, it was the most produced and used British field gun and gun-howitzer during the war.
It was introduced into service just before the War started and combined both high-angle and direct-fire abilities, a relatively high rate of fire, and a reasonably lethal shell, with a highly mobile piece. Initial production was slow, but by 1945, over 12,000 had been manufactured. It remained the British Army's primary artillery field piece well into the 1960s, with smaller numbers used in training units until the 1980s. Many Commonwealth 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 field gun and the 4.5-inch howitzer, which had been the main field artillery piece 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 halfway 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 smooth flat surface for the carriage to rotate on using the road wheels, this enabled the gunners to traverse the carriage quickly in any direction.
File:The British Army in the United Kingdom 1939-45 H20971.jpg|right|thumb|A 25-pounder field gun and limber, towed by a Morris Commercial "Quad", crossing a pontoon bridge at Slaght Bridge in County Antrim, Northern Ireland, 26 June 1942
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", 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. The gun was hooked to it and the trailer hooked to the tractor for towing. The gun did not need a limber 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 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 had a third tractor that carried ammunition and towed two ammunition trailers.
The normal gun detachment comprised six men:
- No 1 – detachment commander
- 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
Production
Many different companies manufactured the guns and component parts in the UK. Vickers-Armstrongs 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.Ammunition
The 25-pounder fired "separate" or two-part ammunition – the projectile was loaded separately from the propelling charge in its cartridge case with its integral primer. Typically for a quick-firing gun, the cartridge case provided obturation.There were two types of cartridge. The normal cartridge contained three cloth charge bags. White or blue bags would be removed from the cartridge to give "charge one" or "charge two", leaving all three bags in the cartridge case gave "charge three". The cartridge case was closed at the top with a leatherboard cup. The second type of cartridge was "super", which provided one charge only. The cup could not be removed from the cartridge case. In 1943, an incremental charge of of cordite was introduced to raise the muzzle velocity when firing armour-piercing shot with charge super; this required a muzzle brake to be fitted. Adoption of "upper-register" fire needed more charges to improve the range overlap. This led to the development of the "intermediate increment" of 4oz cordite, which was introduced in 1944. The bags were striped red and white to indicate that they should only be used with charges one and two. When one bag was used with charge 1 it provided charge 1/2. When one was added to charge 2 it provided charge 2 1/3, and two bags, charge 2 2/3. This allowed a range of seven different charges instead of four.
File:Gunners of 'E' Troop, 124 Battery, 151st Field Regiment filling 25-pdr shells with propaganda leaflets, Roermond, Holland, 24 January 1945. B14123.jpg|thumb|right|
Royal Artillery gunners fill 25-pounder shells with propaganda leaflets.
Roermond, The Netherlands, January 1945.
There were many marks of cartridge, mostly differentiated by propellant type. Double-base propellant was the UK standard but one mark used US single-base. However, triple-base nitrocellulose/nitroglycerine/picrite was used throughout the war and eventually replaced all others.
The 25-pounder's main ammunition was the high-explosive streamlined shell with a 5/10 CRH ogive and boat tail. The explosive filling was of TNT or Amatol. It was also provided with base ejection smoke, star shells, and chemical shells. Incendiary and coloured flare shells were developed but not introduced into service, and smoke shells were sometimes reloaded with propaganda leaflets or metal foil "window". The UK did not develop a WP smoke shell for the 25-pounder.
For anti-tank use, the 25-pounder was also supplied with a limited amount of solid armour-piercing shot, later replaced with a more potent version with a ballistic cap. The AP shot was fired with maximum charge, charge No. 3, super, or super with Super increment depending on the ordnance mark, as muzzle velocity was critical in direct fire for penetration and a flat trajectory.
A shaped charge anti-tank shell was under development in Canada, but the introduction of the three-inch calibre QF 17-pounder, an anti-tank gun, in 1944 ended its development. After the Second World War, the UK replaced AP shot with a HESH shell. Coloured marker shells were also developed but not introduced.
The standard fuze was No 117 direct action. No 119 was also used. Combustion or mechanical time fuzes were used with base ejection shells and mechanical time with graze were used with HE. Proximity fuzes were used from the end of 1944 and subsequently replaced by CVT fuzes.
British service
The 25-pounder was the main field artillery weapon used by British Commonwealth and colonial infantry and armoured divisions of all types during the Second World War. It was also used by the RAF Regiment in North Africa. Throughout the war, each British-pattern infantry division was established with 72 25-pounders, in three field artillery regiments. Armoured divisions were eventually standardised with two field artillery regiments, one of which was self-propelled. Before mid-1940, each regiment had two batteries of twelve guns; after that date, regiments changed to batteries of eight guns and added a third battery, a process that was not completed until early 1943. In the late 1950s, the British Army reverted to batteries of six guns. Field artillery regiments had two batteries of 25-pounders and one of 5.5 inch guns.The early 18- and 25-pounders had been towed in the field by the Morris CDSW or the earlier Vickers Light Dragon Mk. III, a tracked vehicle derived from the Vickers DA50 which was also the basis of the Bren or Universal Carrier. Throughout most of the Second World War, the 25-pounder was normally towed, with its limber, behind a 4×4 field artillery tractor called a "quad". These were manufactured by Morris, Guy and Karrier in England, and, in greater numbers, as the Canadian Military Pattern field artillery tractor by Ford and Chevrolet in Canada. In the 1950s, the British Army replaced the various "quads" with a new Bedford three-ton gun tower fitted with a specialist body.
In 1941, the British Army improvised a self-propelled 25-pounder named the Bishop, on the chassis of the Valentine tank. This mount proved unsatisfactory and the Bishops were replaced in 1942 by the American M7 Priest, which did not use the 25-Pounder complicating the supply of ammunition in the field. The Priests were replaced in 1944 by the Sexton, which used the 25-Pounder. The Sexton was designed, and mostly manufactured, in Canada and was the result of mounting a 25-pounder on a Ram or Grizzly tank chassis.
By Second World War standards, the 25-pounder had a smaller calibre and lower shell-weight than many other field-artillery weapons, although it had longer range than most. It was designed for the British practice of suppressive fire, not destructive fire that had proved illusory in the early years of the First World War. Nevertheless, the 25-pounder was considered by all to be one of the best artillery pieces in use. The effects caused by the gun in the North-West Europe Campaign of 1944–1945 made many German soldiers believe that the British had secretly deployed an automatic 25-pounder.
In UK service, during the 1960s, most 25-pounders were replaced by the 105mm Abbot SPG, some by the Oto Melara 105mm pack howitzer, and the remainder by the 105mm L118 light gun. The last British military unit to fire the 25-pounder in its field role was the Gun Troop of the Honourable Artillery Company on Salisbury Plain in 1992.