High Quality Content by WIKIPEDIA articles! The Ordnance Quick-Firing 17 pounder (or just 17 pdr) was a 76.2 mm (3 inch) gun developed by the United Kingdom during World War II. It was used as an anti-tank gun on its own carriage, as well as equipping a number of British tanks. It was the most effective Allied anti-tank gun of the war. Used with the APDS shot it was capable of defeating all but the thickest armour on German tanks. It was used to `up-gun` some foreign-built vehicles in British service, notably the Sherman Firefly, giving British tank units the ability to hold their own with their German counterparts. In the anti-tank role it was replaced by the 120 mm BAT recoilless rifle after the war. As a tank gun it was succeeded by the 20 pounder.