In the late 1940s, the British War Office (WO) was concerned that – after the debut of the IS-3 in 1945 – the Soviet Union would continue to develop heavily armored tanks. As such, the War Office filed a requirement for the development of a gun capable of defeating a 60-degree sloped plate, 6 inches (152 mm) thick, at up to 2,000 yards (1,830 meters), and a suitable vehicle to carry it.
This requirement led to the development of the ‘Ordnance, Quick-Firing, 183 mm, Tank, L4 Gun’, the largest purpose-built anti-tank gun to have ever been created. It was intended that this gun would be mounted on a new ‘Heavy Gun Tank’ based on the FV200 series chassis. This was designated the ‘Tank, Heavy No. 2, 183 mm Gun, FV215’.
A project was also launched to find a way to get the gun into action quickly on an existing hull. This could then be constructed quickly should the Cold War turn hot before the FV215 was ready.
This is where the FV4005 project comes in.
The Quest for Firepower
The development of the L4 started in 1950, and was aimed at increasing the firepower of the ‘Heavy Gun Tanks’. This was a uniquely British designation that was not governed by tank weight, but the size of the gun. A requirement was formulated for a tank armed with a gun capable of defeating a 60-degree sloped plate, 6 inches (152 mm) thick, at up to 2,000 yards (1,830 meters), a feat impossible even for the powerful 120 mm L1 gun of the FV214 Conqueror. By 1950, Major General Stuart B. Rawlins, Director General of Artillery (D.G. of A.) had concluded that there was no gun available with that level of ballistic performance and an investigation was launched. Initially, the British Military looked at the development of a 155 mm gun that would be standardized with the USA. However, even this lacked the required punch and, as such, 6.5 and 7.2 inch (165 and 183 mm respectively) High-Explosive Squash Head (HESH) shells were looked at.
At this time, the British Army came to the conclusion that a ‘kill’ did not necessarily mean the complete destruction of an enemy vehicle, and just damaging it was enough to take it out of action was enough. For example, a blown-off track is seen as a kill as it took the enemy vehicle out of action; today this is known as an ‘M’ (Mobility) kill. A ‘K’-Kill would be the destruction of a vehicle. The term used for this method at the time was ‘disruption not destruction’. The 6.5 in/165 mm HESH was not thought to be powerful enough to ‘kill’ a heavily armored target in this manner unless it hit bare armor plate. Attention, therefore, turned instead to the larger 7.2 in/183 mm shell which – Maj.Gen. Rawlins thought – would be powerful enough to render the target inoperable, and therefore ‘kill’ it, wherever it impacted.
The projected gun was designated the 180 mm ‘Lilywhite’. The background of this name is unknown. It may be an interpretation of the ‘Rainbow Code’ used by the WO to identify experimental projects. The ‘Red Cyclops’ flame gun attachment for the FV201, and the ‘Orange William’ experimental missile are examples of this. If this was the case, however, the name should be ‘White Lilly’. It may even simply be named after a Lieutenant Colonel Lilywhite of the Royal Army Ordnance Corps. It must be said that this is all speculation, and no evidence currently exists to support the theory.
It was not until December 1952 that the designation of the gun was officially updated to 183 mm. The design of the gun was accepted and was serialized as the ‘Ordnance, Quick-Firing, 183 mm, Tank, L4 Gun’. In reality, only the HESH shell underwent further development and the number of charges was dropped to one. The 183 mm L4 became one of the largest and most powerful tank guns in the world.
Background of the Project
From the start, the FV215 was the intended mount for the 183 mm gun, with development starting around the same time as the gun in 1950. The vehicle was based on the FV200 series chassis, with similarities to the FV214 Conqueror. The turret, however, was moved to the rear of the vehicle. The turret was capable of full 360-degree traverse, but it had a limited firing arc due to the size and power of the gun. This ‘Heavy Gun Tank’ would take a while to develop, so, in November 1950, the WO filed a requirement for a stop-gap vehicle capable of carrying the weapon into service should hostilities erupt before the completion of the FV215. A similar connection can be found with the Conqueror and the FV4004 Conway.
Following the end of General Rawlins’ investigation, and with some degree of urgency to get the 183 mm gun into service as quickly as possible, a carrier design was finalized, as this extract from a 1951 ‘AFV Development Report’ describes:
“A limited traverse, lightly armoured S.P. mounting based on the Centurion hull and weighing some 50 tons[*]. This would be known as F.V.4005 and could be in production by December 1952. Because of the use of parts in existing production, it was considered that quick limited production could be achieved. It was also clear that much would be learned about the hitherto unknown art of mounting so large a gun as an S.P. mounting.”
*50 long tons. Long tons are a unit of mass unique to the United Kingdom; for ease, it will be shortened to ton when used again. 1 long ton is equal to about 1.01 metric tonnes, or 1.12 US ‘Short’ tons.
The design of the vehicle would be held in limbo, ready to go into production if necessary. This stopgap vehicle would be based on the Centurion of the FV4000 series, with the original turret removed. The vehicle would go through two ‘Stages’ or ‘Schemes’. ‘Stage 1’ was built to test the gun and its mount on the Centurion chassis. The ‘Stage 2’ was a finalized design and would be the production standard. The vehicle was given the designation of ‘Heavy Anti-Tank, SP, No. 1’ – ‘SP’ standing for ‘Self-Propelled’. Officially, the FV4005 was never given the traditional British ‘C’ name such as the FV4101 Charioteer and FV4004 Conway before it. However, extensive account files of Vickers Ltd. from 1928 to 1959, shed some light on what it may have been. This particular extract – graciously provided by researcher Ed Francis – is from December 1952:
“Design and manufacture of equipment for mounting 180 mm gun on “CENTAUR” Tank – FV4005. Trials have now been carried out at Ridsdale and certain modifications to design have been found necessary… ”
In total three prototypes were ordered – a single Stage 1, and two Stage 2s. The FV4005 would fill the role of a ‘Heavy Gun Tank’. As such, the vehicle would engage targets from long-range, firing over the heads of attacking lighter tanks.
The Centurion Hull
The Centurion was chosen as the basis for this vehicle and three Mk. 3 hulls were removed from service for the prototype development. Other than the removal of the turret and various small additions, the hull would remain mostly unaltered. Armor on the hull remained the same thickness, with about 3 inches (76 mm) at roughly 60 degrees on the front slope. A 650 hp Rolls-Royce Meteor petrol engine, located at the rear of the vehicle, propelled the tank. The Centurion used a Horstmann style suspension, with 3 bogies per side carrying 2 wheels each. The drive sprocket was at the rear with the idler at the front. The driver was located at the front right of the hull.
Details of the 183 mm L4
Just a small number of the ‘Ordnance, Quick-Firing, 183mm, Tank, L4 Gun’ were built, but it is unclear just how many. Records suggest at least 12 were built. Unfortunately, the exact length of the 183 mm gun is currently unknown, but it was somewhere in the region of 15 feet (4.5 meters) long. It was fully rifled with a large ‘bore-evacuator’ (fume extractor) placed roughly half-way down its length. The gun alone weighed 3.7 tons (3.75 tonnes).
High-Explosive Squash Head (HESH) was the only ammunition type to be produced for the 183 mm gun. Both the shell and the propellant case were of gargantuan proportions. The shell weighed in at 160 lbs. (72.5 kg) and measured 29 ¾ inches (76 cm) long. The propellant case weighed 73 lbs. (33 kg) and measured 26.85 inches (68 cm) long. The case contained a single charge that propelled the shell to a velocity of 2,350 fps (716 m/s). When fired, the gun produced 86 tons (87 tonnes) of recoil force and had a recoil length of 2 ¼ feet (69 cm).
HESH shells have an advantage over regular kinetic energy rounds as their effectiveness does not decrease with distance. This shell works by creating a shockwave on detonation. Once this wave reaches a void, it reflects back. The point at which the waves cross causes tension feedback which rips apart the plate, carrying a scab with approximately half the kinetic energy forwards, scattering shrapnel around the interior of the target. Test firing of the L4 against a Conqueror and a Centurion proved how powerful the round was. In two shots, the 183 mm HESH shell blew the turret clean off the Centurion, and split the mantlet of the Conqueror in half. HESH could also serve as a dual-use round just as capable of engaging enemy armor as for use as a high-explosive round against buildings, enemy defensive positions, or soft-skinned targets.
In a 1951 Ministry of Supply: Fighting Vehicle Division ‘AFV Development Report’ – regarding the development of an AFV mounting of the 183 mm gun – the ‘Stage’ or, ‘Scheme 1’ is described as such:
“Embodies a concentric recoil system in a mounting in trunnions on an undercarriage, the whole of which rests on the existing turret race rings. No crew protection is provided and one prototype only will be made to obtain experience of firing such a large gun from the Centurion hull.
It is anticipated that although all round traverse will be possible, firing will be confined to a limited angle forward on either side of the fore and aft line.
Prototype should be completed by 31st December, 1951”
The Stage 1 was built as a test vehicle, as such, it lacked a few components. On the Stage 1, a bespoke platform was constructed that was installed over the original turret ring. This platform was a solid floor, did not incorporate a basket, and was not, in any way, enclosed. The L4 gun was installed in a rigid mount and was completely fixed in elevation. The platform was capable of full horizontal traverse, but firing would be restricted to a limited arc over the front and rear of the vehicle. As mentioned in the report, the gun used a concentric recoil system. This utilized a tube placed around the breech end of the barrel, acting as a space-saving alternative to traditional recoil cylinders.
Space on the platform was limited, as such, there were only positions available – presumably – for the gunner and loader. The gunner was seated on the left of the gun in a well-padded seat complete with a back-rest. Behind him was a large rack for ammunition stowage. The fact that the gun was fixed in elevation allowed the installation of a mechanical ‘loading assist’ device to help the loader handle the combined 233 lb (105.5 kg) weight of the ammunition by aligning it with the breach. This was not an automatic loader as it lacked a rammer. There was no seat for the loader. The driver’s position – the front right of the hull – was unchanged.
The only other changes to the Centurion hull were the addition of a large recoil spade at the rear and a large folding travel lock or ‘gun crutch’ to use the British term. The spade was used to transfer recoil forces from the chassis directly to the ground, easing the strain on the suspension. When the vehicle was in position, it would be lowered to the ground. When the gun was fired, the spade provided a back-stop by digging into the ground.
The ‘Stage/Scheme 1’ was subjected to numerous firing trials. Despite some issues with the concentric recoil system, the trials were a general success. Work then progressed to the ‘Stage/Scheme 2’ vehicle.
In the same 1951, Ministry of Supply: Fighting Vehicle Division ‘AFV Development Report’, the ‘Stage/Scheme 2’ was described as the following:
“Embodies two conventional recoil systems with a hydropneumatic recuperator and an independent run out control. Undercarriage similar to above [Stage 1] but of fabricated construction.
A superstructure for crew protection will be provided but weight considerations will preclude more than a limited degree of splinter protection.
A sight is being designed in which the body is fixed with relation to the gun mounting, and internal moving parts apply angle of sight, target elevation and correction for trunnion tilt. The range scale is visible in the sight eyepiece.
Layout designs have been prepared and details will be completed shortly.
A prototype should be available by March, 1952.”
The Stage 2 was built closest to what a production version of the FV4005 would consist of. As such, a number of changes were made between the two Stages. The biggest change was the design and construction of a fully enclosed turret to the form of little more than a large box. The loading assist for the loader was also deleted, and the concentric recoil system was replaced by a hydropneumatic type.
The turret was welded and fabricated from ½ inch (14 mm) thick steel and was there to protect the crew from small arms fire and shell splinters. As this was intended to be a second line vehicle that would keep out of the range of enemy AFVs, the FV4005 did not need really thick armor. Also, with the addition of this impressive gun, the chassis and engine could not take any extra weight. The turret was split into two parts: a sloped face and a completely boxed rear end. The turret face was mantletless, with a large face-plate angled at a very shallow angle. The cheeks were also slightly angled. These angled sections terminated in completely vertical turret walls and a flat roof. The roof stepped up as the rear section of the turret was taller and box-like, with external structural ridges. Internally, this rear section was where the ammunition was stowed against the walls. In total, 12 rounds were carried.
There were two hatches on the roof and one large door on the rear. The roof hatches were two-piece and, in front of them, were two single periscopes installed in the turret roof. The large rear door was used for crew access, but it was also used for ammunition resupply via a winch and rail. Charges would be placed on the rail and then winched into the turret. Turret crew would consist of four men including the gunner and commander. As the loading assist of the Stage 1 was deleted on the Stage 2, two loaders were required. One loader would handle the charge, the other the projectile.
On the turret face, to the left of the gun, was a large square bulge. This was the housing for the primary gun sight. The particulars of this sight are unknown, however, there is a suggestion that it was based on the TZF-12A of Panther fame. This, however, cannot be corroborated. While the turret was capable of full 360 degrees horizontal traverse, firing was limited to a limited arc over the front and rear of the vehicle. This was a safety feature necessitated by the power of the gun.
Like the Stage 1, the Stage 2 featured a recoil spade installed at the rear of the vehicle. However, on the Stage 2, a hand-cranked winch was installed on the rear of the vehicle to lower the spade.
Like the Stage 1, the Stage 2 went through a number of firing trials. Where the Stage 1’s concentric recoil system suffered some faults, the Stage 2’s more typical hydro-pneumatic system operated without issue. In total, 150 rounds were fired during the tests at Ridsdale, Northumberland. In a 1955 Fighting Vehicle Division ‘AFV Development Liaison Report’ of the Ministry of Supply it is stated that: “General functioning [of the Stage 2] has proved satisfactory”.
Despite the general success of the project, the FV4005 suffered much the same fate as the FV215. The feared Soviet heavy tanks, like the IS-3, which these vehicles were designed to defeat, were not being made in the massive numbers expected, indicating a shift in policy to lighter, more maneuverable, and more lightly armored tanks. The need for ‘Heavy Gun Tanks’ like the Conqueror, FV215 and the FV4005 stand-in, from this perspective, was simply becoming absent. Other changes were also taking place as technology-wise, larger caliber guns with their huge ammunition were becoming obsolete by improved anti-armor performance of smaller guns and by the appearance of a new generation of accurate Anti-Tank Guided Missiles (ATGM).
The FV4005 project was officially canceled in August 1957, around the same time as the FV215. The three constructed prototypes were divided between various establishments. The Stage 1 was given to the Shoeburyness Proof and Experimental Establishment where the turret was removed and the Centurion hull returned to service. One Stage 2 was offered to the Royal Military College for Science, while the Fighting Vehicle Research and Development Establishment (FVRDE) kept the other Stage 2. The Centurion chassis were also likely returned to service. At some point, one of the turrets found its way to The Tank Museum, Bovington, where it sat alone for a number of years before being mated with a spare Centurion hull owned by the Museum. The vehicle now sits as a ‘Gate Guardian’ outside the museum, alongside a Sherman Grizzly.
Illustration of the FV4005 Stage 1 with the open top gun platform, produced by Pavel Alexe.
Illustration of the FV4005 Stage 2 with enclosed turret, produced by Pavel Alexe, based on work by David Bocquelet.
Both Illustrations were funded by our Patreon campaign.
Specifications (Stage 2)
|Dimensions (L-W-H)||7.82 (without gun) x 3.39 x 3.6 m
(25’7″ x 11’1″ x 11’8”)
|Total weight||50 tons|
|Crew||5 (driver, gunner, commander, x2 loaders)|
|Propulsion||Rolls-Royce Meteor; 5-speed Merrit-Brown Z51R Mk. F gearbox 650 hp (480 kW), later BL 60, 695 bhp|
|Speed (road)||Apx. 30 km/h (19 mph)|
|Armament||QF 183 mm (7.2 in) L4 Tank Gun|
|Armor||76mm @ 60º upper glacis. Turret, 14mm all over.|
2011.2891: Ministry of Supply: Fighting Vehicle Division, AFV Development Progress Report, 1951, The Tank Museum, Bovington
2011.2896: Ministry of Supply: Fighting Vehicle Division, AFV Development Liaison Report, 1955, The Tank Museum, Bovington
2011.2901: Ministry of Supply: Fighting Vehicle Division, AFV Development Liaison Report, 1957, The Tank Museum, Bovington
Vickers Ltd. Account Records, 1928 to 1959 (Provided by researcher, Ed Francis)
Bill Munro, The Centurion Tank, The Crowood Press
Pat Ware, Images of War Special: The Centurion Tank, Pen & Sword Books Ltd.
Simon Dunston, Haynes Owners Workshop Manual, Centurion Main Battle Tank, 1946 to Present.
Simon Dunston, Osprey Publishing, New Vanguard #68: Centurion Universal Tank 1943-2003
David Lister, The Dark Age of Tanks: Britain’s Lost Armour, 1945–1970, Pen & Sword Publishing