Ordnance, B.L. 4,5inch medium field gun Mk.2 on carriage 5,5inch Mk.2 The 4.5-inch Gun was one of the two British medium guns of World War 2, which both used the same carriage, the other being the 5.5-inch. The original Mk 1 gun was developed in the mid 1930s and used a modified 60-pdr carriage, most were lost in France in 1940 but some served in N. Africa. The 4.5-inch was the replacement for the 60-pr Gun, its primary role was counter-battery fire. It was only used by British and Canadian regiments in Europe and N.Africa. It was withdrawn from service at the end of the war.