Cold War, Experimental, United Kingdom

REVISTED: FV4005 and its 183 mm Cannon

In the early Cold War, Britain developed a vehicle with the largest tank-killing gun ever made: the FV4005. Mounting a 183 mm rifled gun on a Centurion hull, the FV4005 was designed specifically with the brute force required to knock out Soviet tanks.

It was expected to fight an enemy that had massive numbers of heavily armored tanks. The gun had been designed for the FV215, a more rounded design, but as that was delayed, it was mounted on a Centurion hull.

In essence, the FV4005 was an insurance policy to ensure the UK had a tank capable of killing whatever the Soviets would throw at them if war ever began.


Background of the FV4005

As we did with the FV215, we need to go back some time to properly explain why the rather absurdly proportioned FV4005 was ever needed.

We travel back to September 1945 – the Axis had been defeated, and the Allies celebrated their victory across the world.

However, despite fighting for the same cause throughout the war, different ideologies, ambitions, and territorial gains mean that the Soviet Union and Western Allies are now enemies, and cracks in their relationship are already showing.

IS-3 heavy tank armored shape.
The IS-3 was a great departure from typical Second World War designs, but it was poorly built and suffered from quite severe reliability and quality issues. Image by Alf van Beem.

At the Berlin Victory Parade that month, the Soviet Union unveiled a new generation of heavy tank; the IS-3. This monstrous machine was low and carried a huge gun and extremely thick armor. It was assumed that the massive manufacturing power of the USSR would allow for tens of thousands of IS-3s to be built.

Although the IS-3 was actually found to be a pretty bad tank (the real threat was tanks like the T-54), at the time the Allies had no vehicles that could counter it and were afraid.

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In response, they began developing tanks capable of killing the IS-3 and other Soviet tanks that may come after it. France developed the AMX-50, the US created the M103, and Britain made the Conqueror.

The Conqueror is intrinsic to the FV4005’s story.

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The Conqueror itself is a fascinating machine, born from the Second World War-era A45, which was renamed to FV201 after the war.

The FV201 was too lightly armed, having only been equipped with a 20-pounder (the same as Centurion), so in 1949 the design was modified to receive a new turret and a large 120 mm gun to help deal with the newer Soviet tanks.

This caliber was used by all three of the Allies’ heavy tank projects (AMX-50 and M103).

Conqueror heavy gun tank.
The Conqueror was developed from the earlier FV201 (A45).

The FV201’s hull was shortened, a crew member was removed and more armor was added. This new vehicle became the FV214 Conqueror. As the Conqueror’s hull was derived from FV201 work moved quickly, with the hull ready for trials in the early 1950s.

The turret, however, was far from ready.

Remember that the tank’s development was on the clock, as if war broke out with the USSR 120 mm-armed gun tanks would be desperately needed.

The Conqueror’s hull was mated with a Centurion III turret (resulting in the FV221 Caernarvon) and tested thoroughly in troop trials while the proper turret was developed.

FV221 Caernarvon.
This is an FV221 Caernarvon. By mounting a Centurion turret on the Conqueror’s hull, the hull could be tested in troop trials.

Meanwhile, a plan B was created in case the Conqueror’s turret was not ready in time for a conflict. This backup consisted of mounting the Conqueror’s 120 mm gun onto a Centurion.

This gun was fitted into a primitive, boxy turret, resulting in the FV4004 Conway. Should war break out, the FV4004 would serve as a stopgap until completed Conquerors entered service.

However despite all this, there were concerns that even the Conqueror’s 120 mm gun would struggle against the IS-3 at medium to long ranges. 

FV4004 Conway survivor today.
This is the surviving FV4004 Conway, currently stored at The Tank Museum in Bovington.

Britain wanted a tank gun that could penetrate 152 mm (6 inch) of armor angled at 60 degrees from a range of 2,000 yards.

To do this, they needed a really big gun.

It was established that a HESH-firing gun 180 mm in caliber was needed, and was to be fitted onto the FV200 chassis (same as the FV201). HESH (high-explosive squash-head), is a type of ammunition that contains a large explosive charge which flattens against armor before detonating.

The wide surface area of the charge before detonation sends shockwaves into the armor, which then impact each other as they rebound and overload the tensile strength of the metal.

A HESH round diagram.
A HESH round cutaway drawing. The inert padding absorbs some of the impact energy and allows the explosive filler to squish against the armor plate. The fuse is mounted at the rear of the filler so it triggers after the filler has flattened.

After being overloaded, a scab of armor detaches from the rear of the plate that will then proceed to bounce around inside the tank.

HESH rounds are useful because they do not rely on speed, unlike conventional armor-piercing rounds. This means that their effective range is higher. They also have the added benefit of simply containing a lot of explosives; this can damage optics, blow off tracks, and start fires. They are also incredibly useful against soft targets.

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This type of ammunition fired from a 180 mm gun would be so devastating that even glancing hits would be enough to put a tank out of action.

Instead of developing an entirely new gun, the BL 7.2 inch (182.9 mm) field gun was modified for use inside a tank. 

FV215 model.
A scale model of the planned FV215. This was to be a heavily armored tank, with a rear-mounted turret and a centrally-mounted engine.

This new gun was designated Ordnance, Quick-Firing, 183 mm, Tank, L4 Gun and was to fire the L1 183 mm HESH round weighing in at around 200 lbs. No armor-piercing or high-explosive anti-tank rounds were made for this gun, it was to fire HESH only.

The vehicle itself was named the FV215 (Tank, Heavy No. 2, 183 mm Gun, FV215), and was a large, heavily armored machine that would weigh around 60 tons.

It was to feature up to 254 mm of armor on the front, and was powered by a V12 Meteor engine.

FV215 right side.
The FV215 was never built. The need for it disappeared before any were built.

Note: this tank was never called the “FV215b (183)”, it was simply designated FV215. Also, it was classed as a tank, not a tank destroyer.

However, as with the Conqueror, the FV215 would take a while to be ready, so yet another backup plan was made to ensure the gun would be on the battlefield in time.

The 183 mm gun was to be mounted on the Centurion to get it into service quicker, creating the FV4005.

The FV4005

This was a similar arrangement to the Conqueror’s backup mentioned earlier, FV4004. Like that tank, the FV4005 was much simpler and could enter service quickly should a conflict begin before the FV215 was ready.

The FV4005 was known also known as “Centuar” at the time.

Of course, the monstrous 183 mm was quite a jump from the 76.2 mm gun the Centurion was originally built with. The Centurion hull was rated for around 50 tons, so the FV4005 was unable to carry both the gun and thick armor like the FV215.

BL 7.2 inch howitzer.
The BL 7.2 inch field gun. The FV215 and FV4005’s 183 mm gun was developed from this weapon.

As a result, the FV4005 would be limited to long-range work out the way of enemy fire.

In 1952, Vickers noted that the design and manufacturing of equipment for mounting the gun on the FV4005 had been done. And before long the 183 mm gun was tested in firing trials against static targets.

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One of these targets was a Conqueror fitted with spaced armor. This vehicle is now incorrectly known as the “Super Conqueror” – this tank was simply a range target, not a functioning vehicle.

FV4005 Apparel Ad.

Regardless, the huge HESH rounds cracked the Conqueror’s turret and caused chaos inside. A Centurion was also fired at, with a single round blowing the turret clean off the hull.

There were two main iterations of the FV4005 during its development; Stage 1 and Stage 2. The Stage 1 is sometimes regarded as an entirely separate tank, but it was simply part of the FV4005’s development.

FV4005 Stage 1

FV4005 Stage 1 was primarily a gun test rig to work out the weapon system.

The weapon itself differed from the later model and had a concentric recoil system rather than hydraulic recuperators which caused some problems.

Concentric recoil systems are a type that surround the barrel itself, rather than seperate recoil cylinders attached to the gun.

The gun was exposed to the elements without any armor or covering, and was also fixed to a limited arc to the front and could not elevate up or down.

FV4005 Stage 1.
This is the wild-looking FV4005 Stage 1. The large ring around the gun, near the breach, is the concentric recoil system.

The “turret” contained a gunner and loader.

A spade was located at the rear to stabilise the platform while firing, and a large gun-lock was mounted on the upper glacis plate.

It is often mentioned that it was equipped with an autoloading system, however this is untrue – no such system was fitted.

The ammunition was very heavy so it was stored in a two-part system of round and charge that weighed around 200 lbs in total. The rounds were kept in a drum-type magazine that could be manually turned to align them with the loading tray to ease loading. The cases were stored in a second rack to the left of the gun.

FV4005 Stage 1 close up to the breech and loading mechanisms.
The loading mechanism found in the FV4005 Stage 1. The loading-assist drum can be seen on the right. The box on the left was the propellant storage.

This is a loader assist not an autoloader, but is likely the source of the autoloader missconception.

A rail system could be placed across the back decks to help resupply the vehicle as while passing the large rounds there was a risk of dropping them. Each was loaded onto the small rail and pushed towards the magazines. 

FV4005 Stage 2

The FV4005 Stage 2 was a more matured design, with the gun now protected by a thin metal box 14 mm thick – although this was little more than protection against the weather.

This distinct vehicle is the one most well known by enthusiasts, certainly in part due to featuring in both World of Tanks and Warthunder.

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The loading assist mechanism was discarded, and in its place came an additional loader. The gun also now had conventional, and more reliable hydraulic recuperators instead of the concentric recoil mechanism.

Front of an FV4005.
This is what a real FV4005’s hull looked like. Note the large travel lock on the front armor.

You may sometimes read that when it fired to the sides the FV4005 rocked back 45 degrees. This is quite untrue; not only would this be a colossal design flaw, damaging or even destroying the tank after every shot, but the forces required to do this are far more than any conventional tank gun can offer.

The little box on the rear of the FV4005’s hull contained a winch to raise and lower the spade.

The vehicles went through various tests with around 150 shots being fired. However, as so often happens with military developments, newer technologies were making vehicles like the FV4005 redundant.

FV4005 rear.
FV4005 rear. Note the spade, and spade lifting handle.

While the FV4005 was armed with the largest direct-fire gun ever mounted on a tank, it was heavy, large and quite outdated for its day, relying on sheer brute force to achieve results.

Its gun was devastatingly powerful, but anti-tank guided missiles could do the same job more accurately and at a greater range.

These developments also rendered the targets – the heavy tank – virtually redundant too. These 50-60 ton machines could now be knocked out by a single missile fired from a truck.

FV4005 today.
The FV4005 when it was outside the museum.

The Soviet Union experienced similar changes at this time, with Nikita Kruschev famously favoring missile tanks over heavy tanks, killing off promising tanks like the Object 277 and 777. And so the FV4005 project was cancelled in 1957.

Three FV4005s were built in total: one Stage 1 and two Stage 2s.

Today only a single Stage 2 turret survives, which for a while spent its time on the ground as a children’s play area (I was blissfully unaware what I was playing on at the time) at The Tank Museum in Bovington.

The FV4005's current location.
The FV4005’s current location.

Around 15 years ago the turret was placed on top of a standard Centurion Mk III hull, and the entire assembly sat outside the museum’s exit and was a familiar landmark for locals in the area.

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Interestingly, during the writing of this article, the FV4005 was moved from that location to one of the museum’s yards, indicating they have plans in store for it.