The highlight of Tankfest 2024 was the unveiling of FV4005, a British Cold War prototype tank that had the largest gun ever fitted to a tank. This was the apex of the race to build ever bigger tanks with thicker armour and increasingly powerful guns.

When Germany was defeated at the end of the Second World War in Europe, the Soviet Union displayed their latest tank in the Allied Berlin Victory Parade on 7th September 1945 in for the first time, unveiling the IS-3¹ heavy tank to the world. The IS-3's design, bigger, more heavily armoured and more powerful than any Western tank was a shock to the British military, who realised that they needed to upgrade their own tanks to deal not only with this existing Soviet heavy tank, but any potential Soviet successors with even thicker armour.

Son of a Gun?

With the Iron Curtain descending, and tensions between the USSR and the West rising, Britain decided to design a new tank. While the Centurion² was potentially a match for the IS-3, Britain believed that the Soviets were starting an arms race, and they would need a tank to deal with a more powerful replacement. This would need a gun capable of destroying heavily armoured tanks at a range beyond which any upcoming Soviet tank heavy tank could return fire and mount it in a new chassis. The Royal Ordnance developed such a weapon, the L4A1 183mm calibre gun, which weighed 2.8 tons but was capable of firing a projectile at 2,350 feet per second that would smash through 6-inches (152mm) of armour plate at 60° at 2,000 yards. It was believed any hit from the gun would immediately disable any enemy tank even if it was not outright destroying it. The ammunition it fired were HESH (High Explosive Squash Head) rounds, which weighed up to 72lb - about the weight of a washing machine - and 30 inches (76cm) long. The ammunition was two piece, so after the explosive round an additional propellant case weighing an additional 68lb and further 68cm long. Together the round was 1.5 metres tall.

In November 1950 two stages of prototypes were ordered. These would determine whether it was possible to ultimately up-gun Britain's Conqueror heavy tank then in development, which was designed to carry a 120mm gun. However as Conqueror was not ready, as an interim measure, prototypes were developed in which the new, giant gun would be mounted on an existing Centurion chassis. This would mean by the time the Conqueror was ready, it would be possible to simply mount the new gun on the new tank as the trials would have already been complete.

FV4005

A Centurion Mark III hull was chosen to use for the tests as these were readily-available and reliable. The name FV4005 means Fighting Vehicle, the number 4000 referred to the Centurion and this would be the fifth variation of the Centurion³.

All The World's A Stage

The first, basic prototype was to see whether it was possible to put an open-mounted gun this size on a tank hull and identify issues. Work began in early 1951 and completed in April 1952. Stage 1 was equipped with an autoloader that held five rounds to assist with the weight. It showed that because of the 87-tonnes of recoil force, it was only possible to fire the gun within a limited arc of 45° at the front of the tank. As well as a concentric recoil system around the barrel's breech, a recoil spade or ground anchor, which looked like a bulldozer blade, would be winched down from the back before firing to dig into the ground to help combat the blast force. Trials finished by June 1953, with the report stating that when firing without the recoil spade, the front of the 50-ton tank would lift up by 17 inches and back drop by 10 inches and would be pushed back 10 inches. If fired at 90° the whole tank would be pushed back 2 inches sideways. Repeated firing also bent and sheared internal components - essentially firing the main gun caused the tank to shake itself apart.

This led to the Stage 2 of the FV4005, which had the gun encased in a fully-enclosed turret, though the turret was unarmoured, only 14mm thick to keep the tank under 50 tons, and while capable of keeping out heavy rain and hail, offered no protection from enemy forces. It did mean there was no room for the autoloader in the turret, so loading the gun required two loaders.

The Stage 2 went through extensive trials through 1955 and 1956. A better recoil system was developed in addition to the recoil spade, as Stage 1 trials had shown the recoil was still so powerful that the tank was shaking itself apart. Trials in 1955 were satisfactory. The gun's hitting power was huge, but with the projectile's low velocity meant it was susceptible to crosswind affecting accuracy, and it was only capable of firing two rounds a minute, and with only 12 rounds carried on the tank, the decision was taken in 1957 to cancel the project.

During the early 1950s, Britain and other nations around the world developed anti-tank guided missiles, which were able to do the same job at a fraction of the cost, weight and be mounted in much smaller, more manoeuvrable vehicles or even be carried by infantry. There was no longer a need to develop a major weapons platform when a man with a missile could do exactly the same thing but cheaper and more effectively. Meanwhile, Stalin, the biggest supporter of the heavy tank, had died in 1953; his replacement Nikita Khrushchev ordered the end of heavy tank development.

Similarly, advances in technology made smaller guns and new forms of ammunition more effective. The FV4005 Centurion hull was repurposed and the Stage 2 turret and gun was sent to the Royal Military College of Science in Shrivenham.

Preservation and Restoration

In 1971 the Tank Museum acquired the turret and gun and left it outside the museum to be climbed on by visiting children. In 2007 the turret was mounted on a spare Centurion Mark XII chassis to be used as a gate guardian. In 2023 Joe Hughes led a project to restore the turret with an accurate, running Centurion mark III chassis, using or recreating all the original components⁴. It was intended to restore the vehicle in time for it to run at Tankfest 2024. An appeal was launched on the Tank Museum's website and within 24 hours, all the funds needed had been raised.

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09.09.24 Front Page

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