| Ordnance QF 3 pounder gun Mk I, Mk II | |
|---|---|
 On a Medium Mk II (special) tank at the Royal Australian Armoured Corps Tank Museum, Puckapunyal, Victoria, Australia | |
| Type | Tank gun |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1924–1940 |
| Wars | World War II |
| Production history | |
| Variants | Mk I, Mk II |
| Specifications | |
| Barrel length | 1.5 m (4 ft 11 in) bore (32 cal) or 1.88 m (6 ft 2 in) (40 cal) |
| Shell | 47x351R. 1.47 kg (3 lb 4 oz) shell. |
| Calibre | 47-millimetre (1.85 in) |
| Muzzle velocity | 560 m/s (1,840 ft/s) (40 cal 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 (59 inch) and 40 calibre (74 inch) versions. The weapon only fired a solid shot, and 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 (e.g., Cannone da 47/32) at the start of the Second World War (and quite a few years into it), 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.