120 Mm M1 Gun - History

History

The Army had originally attempted to make a 120 mm design just after the end of World War I, with a prototype being presented in 1924. The system was considered far too heavy and expensive to be useful, and the project slowed down, although it was never canceled outright.

In 1938 the Army started studying its needs for newer AAA systems, and decided to order new systems for both the heavy and super-heavy role. The former was filled by the new M1 90 mm gun, which replaced the earlier M3 3-inch gun then in use, while work on the 120 was dusted off and mated to a new eight-wheel carriage to produce the 4.7-inch M1 when it was accepted in 1940.

Only a small number of 120s were built, about 550 in total. They were mostly used in fixed positions at various points around the continental U.S., although about fifteen were shipped to the Canal Zone to replace the semi-experimental 105 mm T3 gun that had filled this role. Four were sent, perhaps by mistake, to Northern Ireland. No 120 was ever fired at an enemy aircraft. In 1944 the gun was renamed as the 120 mm Gun M1, as metric naming became the standard.

Like the 90 mm, the 120 was typically operated in a battery of four guns, initially with an associated searchlight and SCR-268 radar, and later with the much-improved SCR-584 radar and M10 Director (Military), and M4 Gun Data Computer that automatically laid the guns as well. the M6 Tractor was used as the prime mover.