|Ordnance QF 25 pounder
|Place of origin
||World War II
Rhodesian Bush War
South African Border War
Turkish invasion of Cyprus
Sri Lankan Civil War
|Specifications (Ordnance QF 25 pounder Mk II on Carriage 25 pounder Mk I)
||1,633 kg (3,600 lb)
||4.6 m (15 ft 1 in) (muzzle to towing eye)
||2.47 m (8 ft 1 in)
||2.13 m (7 ft) (width at wheel hubs)
||1.16 m (3 ft 10 in) (trunnion height)
||11.5 kg (25 lb) (HE including fuze)
||87.6 mm (3.45 in)
||Vertical sliding block
||-5° to 45°
(70° with dial sight adapter and digging trail pit or wheel mounds)
||4° Left & Right (top traverse)
|Rate of fire
||Gunfire, 6-8 rpm
Intense, 5 rpm
Rapid, 4 rpm
Normal, 3 rpm
Slow, 2 rpm
Very slow, 1 rpm
||198 - 532 m/s
(649 - 1,745 ft/s)
||12,253 m (13,400 yd) (HE shell)
||Calibrating & reciprocating
The Ordnance QF 25 pounder, or more simply, 25-pounder or 25-pdr, was introduced into service just before World War II, during which it served as the major British field gun/howitzer. Combining high rates of fire with a reasonably lethal shell in a highly mobile piece, it was 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.
The design was the result of extended studies looking to replace the 18 pounder (3.3 inches (84 mm) 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 direct-fire capability of the 18 pounder and the high-angle fire of the howitzer, firing a shell about half way between the two in size, around 3.5–4.0 inches (89–100 mm) of about 30 pounds (14 kg).
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 3.45 inches (87.6 mm) weapon firing a 25 pounds (11 kg). 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 lowered and the gun pulled onto it, providing a flat smooth surface for the road wheels that allowed the gunners to quickly traverse the weapon in any direction.
Unlike the 18 pounder, the 25 pounder used howitzer type variable charge ammunition. For the Mk 1 Ordnance on 18 pounder carriage there were three "charges", Charge 1, 2 and 3 in a single cartridge. The 'proper' 25-pdr, Mk 2 Ordnance on Mk 1 Carriage, also had charge super in a separate cartridge. An increment for charge super was introduced in 1943 to provide higher velocity for anti-tank shot. Subsequently another type of increment was introduced to be added to charges 1 and 2 to provide three additional charge combinations for use with upper register (high angle) fire. The introduction of the increment to charge super was only possible following the addition of the muzzle-brake in the previous year.The 25-pdr 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) because the cartridge case provided obturation (it provided the gas seal in the breech) and was automatically released when the breech was opened.
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 limber ("Trailer, Artillery, No 27"). The gun was hitched to it and the trailer hitched to the tractor when on tow. 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 (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 4 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 items. 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 world wide.
The 25 pounder fired separate ammunition; the projectile and the propelling charge in its usually brass cartridge case with its integral primer were loaded separately. Being a QF gun the cartridge case provided obturation.
There were two types of cartridge. The 'Normal' contained three cloth charge bags (coloured red, white and blue). White and/or blue bags would be removed from the cartridge to give "Charge 1" or "Charge 2", leaving all three bags in the cartridge case gave "Charge 3". The cartridge case was closed at the top with a leatherboard cup. The second type of cartridge was "Super"; it provided charge "Super" only. The cup could not be removed from the cartridge case. In 1943, an Incremental Charge of 5.5 oz (160 g) of cordite (Super plus) was introduced to raise the muzzle velocity when firing AP shot with charge Super; this required that a muzzlebrake was fitted. Adoption of "upper register" (high angle) 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 1 and 2. When one bag was used with Charge 1 it provided Charge 1 1/2. When one was added to Charge 2 it provided Charge 2 1/3, and two bags, Charge 2 2/3. This give a total of 7 charges instead of 4.
There were many marks of cartridge mostly differentiated by propellant type. Double base propellant (nitrocellulose/nitroglycerine) was the UK standard but one mark used US single base (nitrocellulose only). 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 (HE) streamlined shell with a 5/10 CRH ogive and boat tail. It was also provided with base ejection smoke (white and coloured), 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 pdr was also supplied with a limited amount of 20 pounds (9.1 kg) solid armour-piercing (AP) shot, later replaced with a more potent version with a ballistic cap (APBC). 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 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 marked shells (dye and PETN) were also developed but not introduced.
The standard fuze is No 117 Direct Action (DA). No 119 (DA and graze) was also used. Combustion or mechanical time fuzes were used with base ejection shells and mechanical time with graze were used with HE. VT fuzes were used from the end of 1944 and subsequently replaced by CVT fuzes.