OQF 3-pounder gun
The Ordnance QF 3 pounder 2 cwt gun was a 47 mm British tank gun based on the Ordnance QF 3 pounder Vickers naval gun, mounted on Vickers-built tanks in the 1920s and 1930s. The gun was produced in 31 calibre and 40 calibre versions. In British service the weapon only fired a APHE round, but .
It was stated in the requirements of the A6 series of Vickers Medium tanks to have the ability to penetrate the armour of contemporary hostile tanks at a range of 1000 yards. The Vickers Medium Mark I was equipped with the Ordnance Quick Firing 2cwt Mark I version of the weapon, whilst from the Vickers Medium Mark II the Mark II version of the 3-pounder was utilized.
Even though other European countries still fielded similar weapons at the start of the Second World War, due to its comparatively low muzzle velocity the 3-pounder was considered obsolete by the war start by the British, with the Ordnance QF 2-pounder replacing it as the standard tank gun of British tanks.