47 mm Model 1931 anti-tank gun

47 mm Model 1931 anti-tank gun C.47 F.R.C. Mod.31
An example from the Royal Museum of the Armed Forces and Military History, Brussels
Type	Anti-tank gun
Place of origin	Belgium
Service history
In service	Second World War
Used by	Belgium Nazi Germany Kingdom of Hungary
Production history
Designed	1931
Manufacturer	Fonderie Royale de Canons
No. built	750+
Specifications
Weight	515 kg
Caliber	47 mm
Elevation	- 3° to +20°
Traverse	20° Left/20° Right (Towed variant)
Muzzle velocity	675 m/s (AP) / 450 m/s (HE)
Maximum firing range	2,000 m

The Royal Cannon Foundry 47mm anti-tank gun Model 1931 (French: Canon anti-char de 47mm Fonderie Royale de Canons Modèle 1931, abbreviated to C.47 F.R.C. Mod.31) was an artillery piece developed in 1931 for the Belgian army which saw widespread service in the Battle of Belgium in 1940. It was colloquially known as the "'Quat'sept", after its 47 millimetres (1.9 in) caliber, by the Belgian soldiers that used it.

It was developed by the firm F.R.C., the Herstal-based Fonderie Royale de Canons, not to be confused with the French F.R.C.

Both infantry and light troops (cavalry units, cyclist units,...) versions of the gun were produced with minor variations: the light troops version had pneumatic tires for greater road mobility, while the infantry versions had heavier but more durable full-rubber tires. The gun was also able to be incorporated into fixed defences and bunkers, including the Belgian fortifications at the Albert Canal. They were also fixed to the T-13 tank destroyer and the 'Canon antichar automoteur Vickers-Carden-Loyd Mk.VI'.

Regarding its time of development, the '47' had an impressive performance, especially in comparison to contemporary German or French designs – respectively the 3.7 cm Pak 36 and 25 mm Hotchkiss anti-tank gun. In medium range armor penetration it even outperformed the British Ordnance QF 2-pounder: armor-piercing rounds could penetrate 47 millimetres (1.9 in) of armored steel at a range of 300 metres (980 ft). This was largely due to the heavy caliber with a shell weight of 1.52 kilograms (3.4 lb) for the armor-piercing rounds. However, this performance came at a price: with a total weight of 515 kilograms (1,135 lb), not including ammo or equipment, the 47 mm was a lot heavier than the German Pak 36 (at 327 kilograms (721 lb)) although, with a compact design, the 47 mm was easier to conceal. Repositioning was aided by Vickers Utility B armoured tractors in infantry divisions or the Ford Marmon Herrington armoured tractor in cavalry units.

Over 750 47 mm guns were in service in the Belgian army at the time of the German invasion in 1940. All active and first reserve infantry units, cavalry units and units of the border guards were equipped with the gun, while the second reserve units had to make do with older anti-tank rifles. Every infantry regiment consisted of 3 battalions of rifle infantry and a single heavy arms battalion. This in turn consisted of three heavy weapon companies, one of which was equipped with 12 47 mm guns. Given its good armor penetrating capabilities, the 47 mm could penetrate the armor of the German Panzer III and Panzer IV tanks from a range of over 500 metres (1,600 ft). Reports of panzers knocked out by the 47 mm during the Battle of Belgium do exist, but in general the bulk of the Belgian army was deployed in the north of the country, on the flat terrain of Flanders, and not in the hilly terrain of the Ardennes in the south, which was regarded as impenetrable but nonetheless served as the primary route of invasion for about 2,500 German panzers.