Ordnance QF 6-pounder 7-cwt Anti-Tank Gun, Marysville, New Brunswick. The Ordnance QF 6-pounder 7-cwt Anti-Tank Gun was a British 57-mm gun used from the middle of the Second World War, as well as the main armament for a number of armoured fighting vehicles. It replaced the 2-pounder Gun in the anti-tank role. Produced in Canada, the 6-pounder continued to be used for many years after the war.