outside army bases in Pakistan. The Irish Army acquired six 6-pounder anti-tank guns in the late 1940s. The US 57 mm M1 gun is popular with modern-day cannoneers, as there is a relatively good supply of shell casings and projectiles. The gun is also reportedly still in active military use with some South American countries, and in coastal defence emplacements of outlying island garrisons of the Republic of China Army. During the Biafran War, from 1967 to 1970, both the Nigerian Federal Army and the Biafran armed forces, including some Biafran vessels, used the 6-pdr gun. Variants Mk 1: limited production version with L/50 barrel. Mk 2: first mass-production version. Shortened L/43 barrel was adopted due to the shortage of suitable manufacturing equipment. Mk 3: tank version of Mk 2. Mk 4: L/50 barrel, single baffle muzzle brake. Mk 5: tank version of Mk 4. Molins Class M gun: 6-pounder gun fitted with automatic loader built by the Molins company, a manufacturer of cigarette making machines. It was mounted on the Royal Navy Motor Torpedo Boats and in the RAF Mosquito planes, which were referred to as the "Tsetse". 57 mm Gun M1: US-built version; although based on Mk II, it had the "original" L/50 barrel. Carriage types, British: Mk 1 Mk 1A: different axle and wheels Mk 2: simplified design Mk 3: modified for use by airborne troops Carriage types, US: M1 M1A1: US wheels and tyres M1A2 (1942): improved traverse mechanism, allowing free traverse M1A3 (1943): modified towing hook; the first version to be adopted by the US Army M2 (1944): caster wheel added to the right trail, relocated trail handles, new utility box M2A1 (1945): improved elevation gear Self-propelled mounts Tank gun versions of the 6-pounder were used in Crusader Mark III, Cavalier, Centaur Mk I and II, Cromwell Mk I to III, Valentine Mk VIII to X and Churchill Mk III and IV, and also in the Canadian Ram Mk II and the prototype American Light Tank T7E2. The Deacon wheeled and the experimental Alecto Mk II self-propelled guns also mounted the 6-pounder. Another experimental vehicle armed with the 6-pounder was a 'Firefly' tank destroyer, based on the Morris Light Reconnaissance Car. The only mass-produced vehicle mounting the 57 mm M1 was the M3 Half-track based 57 mm Gun Motor Carriage T48 (also known by its Soviet designation SU-57). The production of the T18E2 armored car,