AMX-US (AMX-13 Avec Tourelle Chaffee)

France (1957)
Improvised Light Tank – 150 Built

In 1956, the French Army and the Direction des Etudes et Fabrications d’Armements (Directorate of Studies and Manufacture of Armaments, DEFA, an institution within the French Military) were looking into affordable methods of modernizing their fleet of aging M24 Chaffee light tanks. One method was to somehow combine France’s new domestic light tank, the AMX-13, with the M24.

The officially designated AMX-US was a result of this. It would ‘mate’ the turret of the M24 with the hull of the AMX-13. The AMX-13 would become one of the world’s most popular light tanks to come out of the Cold War era, appearing in the early 1950s. While this particular variant goes by the official name of ‘AMX-US’, there are many other unofficial names, including ‘AMX-13 Chaffee’ – as it was known by troops – or ‘AMX-13 Avec Tourelle Chaffee (with Chaffee Turret)’.

Just a small number of these vehicles were produced. They initially found service in French Military Units tasked with policing colonies such as Algeria. They eventually found use as driver training vehicles once they were discharged from frontline service.

French Chaffees

After the Second World War, France’s armored force consisted, almost entirely, of US-built vehicles, such as the M4 Sherman, M26 Pershing, and M24 Chaffee (among others). France received these vehicles as aid as part of the Marshall Plan and the Mutual Defense Assistance Act (MDAA). These aid pacts also financed the reconstruction of France’s economy and armed forces from 1948 until the late 1950s. In April 1949, the North Atlantic Treaty was signed, and NATO was born, resulting in the United States extending the MDAA. This resulted in France receiving newer vehicles, such as the M47 Patton II tank.

In total, France would operate around 1,250 M24s which were identical to their US counterparts. It was a small tank at 5.45 meters (16 ft 4 in) long, 2.84 meters (9ft 4in) wide, and 2.61 meters (9ft 3in) tall. It weighed 16.6 tonnes (18.37 tons), utilized a torsion bar suspension, and was armed with a 75 mm gun. The tank had a 5 man crew: Commander, Gunner, Loader, Driver, Bow Gunner. The ‘Chaffee’ was named after WWI US Army General, Adna R. Chaffee Jr.

The French Army deployed its M24 in both the 1954-1962 War in Algeria, and the 1946-1954 First Indochina War. It served with distinction in both theatres but would ultimately end up being fully replaced by the AMX-13.

The AMX-13

Designed and built by Atelier d’Issy les Moulineaux or ‘AMX’, the officially titled Char de 13 tonnes 75 modèle 51 (Tank, 13 tonnes, 75mm gun, model of 1951) – often shortened to Mle 51, was more commonly known as the ‘AMX-13’. The tank was designed in the late 1940s and appeared in service in the early 1950s. It was designed to be a lightweight, highly mobile tank destroyer that could also perform the reconnaissance tasks of a light tank.

It was lightly armored, with the toughest plates being just 40 mm (1.57 in) thick. Its main armament consisted of the 75 mm Canon de 75 S.A. Mle 50, often known simply as the CN 75-50 or SA-50. The design of this gun was derived from the powerful Second World War German KwK 42 gun mounted on the Panther. The gun was mounted in an innovative oscillating turret and was also fed via an autoloading system.

The AMX weighed in at around 13 tonnes (14 tons) and was 6.36 m (20 ft 10 in, with gun) long, 2.51 m (8 ft 3 in) wide, and 2.35 m (7 ft 9 in) tall. It was operated by a 3-man crew consisting of the Commander, Driver, and Gunner. The tank went through many upgrades with many variations based on its highly adaptable chassis. The French Military only retired the AMX in the 1980s, but many other nations retain it in service.

Char Meets Chaffee

In 1956, DEFA and the French Military were investigating ways to efficiently upgrade the aging Light Tank M24. Initially, this led to the mating of the Mle 51’s FL-10 oscillating turret to the hull of the Chaffee. While cheap and feasible, this configuration never went further than trials. This was largely due to a perceived safety issue with the High-Explosive (HE) rounds fired by the CN 75-50 cannon. Inside the FL-10 turret, the CN 75-50 gun was fed via an automatic loading system, which was reloaded externally. If an alternate shell-type needed to be fired, HE, for example, it had to be loaded into the breach manually by the Commander. This was a tricky task in the tight confines of the turret on the standard AMX, made worse by the notoriously sensitive fuze of the HE rounds. This process would be even more dangerous on the smaller hull of the Chaffee. As a result, the inverse of this mounting was decided upon, mounting the Chaffee’s turret on the Mle 51’s hull.

Avec Tourelle Chaffee

By 1957, work on the inverse of mounting the Chaffee turret to the AMX hull had begun. This was seen as a safer and easier alternative. It was also a convenient way of recycling useful Chaffee turrets by separating them from their worn hulls. It also created a vehicle lighter than the regular Chaffee, meaning it was easier to transport.

The M24 turrets went through very little modification for their installation, retaining all the same main features. The only modification necessary was the introduction of an adapter or ‘collar’ to the AMX hull’s turret ring. This was needed as the Chaffee turret had quite a deep basket. The collar granted the basket clearance from the hull floor for uninterrupted, full 360-degree rotation.

Turret Details

The Chaffee turret was a standard design with a typical 3-man crew of the time: Gunner, Loader, and Commander. The Commander sat at the left rear of the turret under a vision-cupola, the gunner sat in front of him. The loader was located at the right-rear of the turret under his own hatch. Armor on the turret was 25 mm (.98 in) thick on all sides, with the gun mantlet being 38 mm (1.49 in) thick. Armament consisted of the 75 mm Lightweight Tank Gun M6 which had a concentric recoil system (this was a hollow tube around the barrel, a space-saving alternative to traditional recoil cylinders). Variants of this gun were also used on the B-25H Mitchell Bomber, and the T33 Flame Thrower Tank prototype. The shell velocity was 619 m/s (2,031 ft/s) and had a maximum penetration of 109 mm. The elevation range of the gun was around -10 to +13 degrees. Secondary weapons were also retained. This included the coaxial .30 Cal (7.62 mm) Browning M1919 Machine Gun, and the .50 Caliber (12.7 mm) M2 Browning Heavy Machine gun which was mounted on the rear of the turret roof.

The AMX Hull

Apart from the adaptor or ‘collar’, the AMX hull went through no alterations. It retained the same dimensions, and forward-mounted engine and transmission. The tank was powered by a SOFAM Model 8Gxb 8-cylinder, water-cooled petrol engine developing 250 hp, propelling the tank to a top speed of around 60 km/h (37 mph). The vehicle ran on a torsion bar suspension with five road-wheels, two return rollers, a rear-mounted idler, and a forward-mounted drive-sprocket. The driver was positioned at the front left of the hull, behind the transmission and next to the engine.

Service

Trials with what would be designated the ‘AMX-US’ were undertaken between December 1959 and January 1960. The vehicle was well received, with an order for 150 conversions being placed by the French military in March 1960. Conversion work was carried out at a plant in Gien, North-Central France.

The AMX-US was operated by a four-man crew, as opposed to the three-man crew of the standard Mle 51, due to the three-man turret of the Chaffee. The AMX-US saw brief service in the War in Algeria – otherwise known as the Algerian War of Independence or Algerian Revolution. They served well, but a few were lost in combat. One known operator was the 9e Régiment de Hussards (9th Hussar Regiment) based in Oran. There is no evidence to suggest they served in any other location with the French military, such as in France or West Germany based regiments.

After the conflict in Algeria, the vehicles were returned to France. They did not last long in active service after this, with many vehicles being repurposed into driver trainers. For this, the vehicles were disarmed, with the 75 mm gun and mantlet removed from the turret face. In its place, a large plexiglass windscreen was installed. In this capacity, the AMX-US stayed in service until the 1980s, when they were finally completely retired. After this, many were ‘sentenced to death’ as range targets or simply scrapped.

Conclusion

The AMX-US is an example of an effective improvisation. It ‘mated’ old technology with new technology, creating a cheap yet effective light tank that did its job without issue. It also solved the problem of what to do with useful surplus and excess material. An interesting observation is that this is the only AMX-based upgrade or conversion that resulted in the hull being used and not the turret – apart from the AMX-13 (FL-11). The M4/FL-10 is a successful example of this.

Due to the AMX-US’ fate, the vehicles are now extremely rare, with almost none surviving. Some, however, do still sit rusting away on military ranges.

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AMX-US ‘Lamarck’ during the Algerian Conflict of the early 1960s. The combination of the Mle 51’s hull with the M24 Chaffee’s turret was achieved with a simple adaptor ‘collar’ placed on the turret ring.

When they were retired from active service, many AMX-US’ were turned into driver trainers. They were completely disarmed, with a large window on the front of the turret replacing the gun and mantlet.

These illustrations were produced by Tank Encyclopedia’s own David Bocquelet.

Specifications
Dimensions (L-W-H)	6.36m (4.88m without gun) x 2.5m x 2.3m (20’9″ (16’0″) x 8’2″ x 7’5″ ft.in)
Total weight, battle-ready	Aprx. 15 tons
Crew	4 (Commander, Loader, Gunner, Driver)
Propulsion	Renault gasoline, 8-cylinder water-cooled 250 hp
Suspension	Torsion arms
Maximum speed	60 km/h (40 mph)
Range (road)	400 km (250 mi)
Armament	75 mm Lightweight Tank Gun M6 .30 Cal. (7.62 mm) Browning M1919 Machine Gun .50 Caliber (12.7 mm) M2 Browning Heavy Machine gun
Armor	Hull 40 mm (1.57 in), turret 38 mm (1.49 in)
Production	150

Sources

M. P. Robinson, Peter Lau, Guy Gibeau, Images of War: The AMX 13 Light Tank: A Complete History, Pen & Sword Publishing, 2019.
Olivier Carneau, Jan Horãk, František Kořãn, AMX-13 Family in Detail, Wings & Wheels Publications.
Steven J. Zaloga, New Vanguard #77: M24 Chaffee Light Tank 1943-85, Osprey Publishing
Jim Mesko, M24 Chaffee in Action, Squadron/Signal Publications
www.chars-francais.net

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