In the early 1950s, the opening years of the Cold War, the western powers were highly concerned with the amount of powerful armor available to the USSR.
In answer to this, the British military developed a ferocious new anti-tank gun, the 183 mm (7.2 in) L4. The race was on to find a suitable mount for this monstrous weapon. It was first proposed to be used as part of the FV215 project. This self-propelled gun (SPG) design was based on the FV200 Universal tank concept. This vehicle, however, did not go further than the mock-up stage.
Designers tried again, this time with a proposal to mount the gun on the chassis of Britain’s trusty new Main Battle Tank, the Centurion. This vehicle would go under the project title of FV4005.
Original blueprint on the FV4005 Stage II – Photo: Andrew Hills/Ed Francis
Design and Development
The FV4005 was a separate project from the Centurion based vehicle, the FV4004 Conway, armed with the 120 mm (4.72 in) L1 gun. The two projects were not related but had the same goals. The FV4005 was fitted with a much larger gun.
Vickers-Armstrong was in charge of the development of the tank. The Centurion chassis chosen for the project was that of the Mk.III. The platform for the gun was made to fit perfectly into the existing turret ring of the hull. Only slight alterations were made to the chassis. A large recoil spade was added to the rear of the vehicle and an equally large travel lock, or “Gun-Crutch” as the British called it, was added to the front.
The recoil spade helped to keep the vehicle in place while firing, meaning the gunner didn’t have to re-adjust after every shot. The travel lock was used to keep the gun from swaying while the vehicle was moving, helping to reduce stress on its components.
Britain’s Biggest Boom-Stick, the 183mm L4
In 1950, work started on the Ordnance Quick Firing 183 mm (7.2 in) L4 gun. At the time, it was the largest and most powerful tank gun in the world. The cannon was based on the 183 mm (7.2 in) BL 7.2 inch howitzer, a WWI era weapon. The gun itself weighed a mighty 4 tons and when fired it produced the equivalent of 87 tons of recoil force.
The L4 was designed to be chambered for only one type of ammunition, HESH (High Explosive Squashed Head). It was separately loading ammunition. The projectile was loaded first followed by the correct propulsion cartridge. Each shell weighed a combined total of 104.8 kg (231 lbs). A shell of this size understandably produced a substantial amount of fumes and smoke inside of the fighting compartment. As such, a large fume extractor was added to the barrel, a relatively new feature at the time.
The 183 mm was tested in live fire trials against a Centurion and a Conqueror. In 2 shots, the 183 blew the turret clean off the Centurion and split the mantlet of the Conqueror in half. In total, the gun fired 150 shells.
The FV4005 Stage I was a relatively simplistic vehicle, serving as little more than a test-bed for the 183 mm L4 gun. The hull of a Mk.III Centurion tank was chosen for the project. The gun was mounted on a platform in the turret ring, completely open to the elements devoid of any armor.
The Stage I, possibly in Workshop 5 (the so-called secret shed at Elswick) – Photo: warspot.ru
The L4 was expected to have a rate of fire of 6 rounds per minute. As mentioned above, the separately loading 183mm HESH ammunition equipped to the FV4005 weighed a combined total of 104.8 kg (231 lbs) each. As such, the gun would require 2 loaders to service the weapon effectively. 6 rounds a minute would still be a hopeless fantasy, however.
To combat this, in an attempt to ease and quicken the loading process, Vickers-Armstrongs developed a mechanized ammunition feed system, similar to that used on the 104-mm Green Mace anti-aircraft gun. Contrary to popular belief, this was not a traditional auto-loader. It was simply a loading assistance device that would help to align the shells and propellant with the breach. The mechanism did not include a rammer.*
Testing highlighted stability issues with the platform when the gun was fired. It was also surmised that the open, unarmored fighting compartment, necessitated by the loading-system, was not worth the price in crew safety. As such, work began on re-working the gun platform.
The Stage I during trials – Photo: Ed Francis
*It should be noted that exact details of whether the Stage I used an auto-loader is a gray area. As such, portions of information are missing from this segment concerning the vehicles weapon. In the not too distant future, we hope to shed light on these areas.
Links, Resources & Further Reading
Archives, The Tank Museum, Bovington, England
Key Publishing Ltd., The Big Gun Centurions, Classic Military Vehicles. Written by David Fletcher.
An article on the FV4005 by Yuri Pasholok on warspot.ru (Russian)
The FV4005 Stage II was the final form of the project. It was designed and built in 1955. The open gun platform was replaced with a large, box-like turret. The loading assistance device was also deleted, in favor of more traditional loading. With the addition of the large, approximately 2-meter high turret, the FV4005 weight climbed to 50 tons.
The FV4005 during trials in 1956. Note the driver in the hull, and the commander at the very top of the turret. Photo: warspot.ru
Despite being an extremely prominent target, the turret armor was only 14 mm (0.55 in) at its thickest. This was easily penetrable even by large caliber machine guns rounds. It also only had enough space to store 12 rounds. These rounds were stored in racks of 6 on each side of the large bustle.
The turret housed 4 crew members. These were the commander on the forward left, gunner on the front right and 2 loaders positioned behind the gun. On the left of the gun, in a small box on the cheek, was a coaxial .30 cal (7.62 mm) machine gun. This was most likely used for ranging rather offensive/defensive fire. There was a large door in the rear of the turret bustle for crew access and ammunition re-supply. The driver was located in the standard position in the hull.
It should be noted that the lack of armor was intentional. This vehicle was designed to engage at long-range, shoot and re-position. Flexibility was slightly hampered by the turret, however. In theory, it was fully traversable. On uneven ground, this was not recommended due to balancing issues with the gun. As such, the vehicle only really had a 90 degrees arc of fire to the left and right.
The Stage II turret being towed to firing trials – Photo: Ed Francis
A rear view of the vehicle. Note the recoil spade and the box above it. This box holds the winch to raise and lower the spade – Photo: Ed Francis
A rear view of the turret showing the rear door open in a display of how ammunition is loaded into the vehicle – Photo: Ed Francis
January 1957 marked the end of the road for the 183 mm armed SPGs, despite admirable performance during trials. The intended role of the vehicles had been overtaken by increasing development of ATGMs (Anti-Tank Guided Missiles). These granted the same, if not better, anti-armor capabilities, with the experiments ultimately culminating in the Malkara and Orange William missile systems.
Work would continue on the gun. Had it have been adopted, the L4 would’ve been succeeded by the 180mm “Lily White”. This only got as far as conceptual stages, however.
The FV4005 Stage II is the only one of these 183mm armed vehicles to survive to this day. The turret is original, but it was mounted on a spare Mk.VIII Centurion hull, not the original it was trialed with. It is missing the recoil spade and travel lock. This “Cut-and-Shunt” representation of the vehicle now sits as a “gate-guardian” at The Tank Museum, Bovington, alongside an M4 Sherman. Its predecessor, the FV4004 Conway is safe and sound in the VCC (Vehicle Conservation Center) at the site.
The 4005 as it stands today out side the Bovington Tank Museum – Photo: warspot.ru
FV4005 Stage II Specifications
|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|
.30 Cal. (7.62 mm) machine gun.
|Armor||120 mm frontal hull armor. Turret 14mm all over.|
Tank Encyclopedia’s own illustration of the FV4005 Stage II by David Bocquelet