47 mm Model 1931 anti-tank gun

The Royal Cannon Foundry 47mm anti-tank gun Model 1931 (Canon anti-char de 47mm Fonderie Royale de Canons (FRC) 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" (Forty-seven) by the soldiers that used it. It was developed by the firm F.R.C., the Herstal-based Fonderie Royale des Canons, not to be confused with the French F.R.C.

Versions
Both infantry and cavalry versions of the gun were produced with minor variations: the cavalry 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 defenses and bunkers, including the Belgian fortifications at the Albert Canal. They were also fixed to the T-13 tank destroyer.

Performance
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 mm of armored steel at a range of 300m. This was largely due to the heavy caliber with a shell weight of 1.52 kg for the armor piercing rounds. However, this performance came at a price: with a total weight of 515 kg, not including ammo or equipment, the '47' was a lot heavier then the German Pak 36 ( combat weight 327 kg). Being a compact design, the '47' was easy to conceal, but as a consequence of its heavy weight and the general lack of mechanization in the Belgian army of 1940, repositioning the gun was a difficult task.

Belgium
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 3 heavy weapon companies, one of which was equipped with 12 47mm anti-tank guns Model 1931. . Given its good armor penetrating capabilities, the '47' could penetrate the 30 mm armor of the German Panzer III and Panzer IV tanks from a range of over 500m. Reports of panzers knocked out by the '47' 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.

Hungary
Several hundred 47 mm guns were captured by the Germans after the battle of Belgium and donated to the Hungarians in 1940-1, to make up for their lack in anti-tank guns during Operation Barbarossa. Their use was limited however due to a lack of spare parts, while the armor penetrating capabilities of these guns had also been surpassed by the Soviet advances in tank construction. Most were relegated to training duties.