120 mm M1 gun

120 mm M1 gun
Виталий Барсов · CC BY-SA 3.0 · source
Name	120 mm M1 gun
Caption	A 120 mm M1 gun on display at Fort Sill.
Type	Anti-aircraft gun
Origin	United States
Service	1944–1960
Used by	United States Army, United States Marine Corps
Wars	World War II, Korean War
Designer	U.S. Army Ordnance Department
Design date	1940–1944
Manufacturer	Watervliet Arsenal
Number	~1,000
Variants	M1, M1A1
Weight	64,000 lb (29,000 kg) emplaced
Length	27 ft 6 in (8.38 m)
Part length	276 in (7.0 m) L/55
Width	16 ft (4.9 m)
Height	15 ft 6 in (4.72 m)
Crew	15
Cartridge	120 × 775 mm R
Caliber	120 mm (4.72 in)
Action	Semi-automatic sliding wedge
Rate	12 rounds per minute
Velocity	3,100 ft/s (945 m/s)
Range	47,000 ft (14,000 m) ceiling; 19 mi (31 km) surface
Max range	57,000 ft (17,000 m) ceiling
Feed	Manual
Sights	M9 gun director, SCR-584 radar

120 mm M1 gun was a heavy anti-aircraft gun developed by the United States during World War II. It was the most powerful anti-aircraft artillery weapon fielded by the United States Army and United States Marine Corps, designed to engage high-altitude bomber formations. The gun saw service in the final year of World War II and later during the Korean War, providing long-range air defense for key installations and fleets.

Development and design

The development of the 120 mm M1 was initiated by the U.S. Army Ordnance Department in 1940, responding to the need for a weapon capable of reaching the altitudes of modern Luftwaffe and Imperial Japanese Army Air Service bombers. The design was heavily influenced by prior work on the QF 4.5-inch gun and incorporated features from the 90 mm M1 family. Primary engineering and manufacturing was conducted at the Watervliet Arsenal in New York. The resulting weapon was massive, requiring a 15-man crew and a complex gun carriage with four outriggers for stability. Its fire control was integrated with advanced systems like the M9 electrical director and the SCR-584 radar, a microwave radar set developed at the MIT Radiation Laboratory.

Service history

The 120 mm M1 entered service in 1944, with initial deployments to protect strategic sites such as the Panama Canal and critical harbors in the United Kingdom. Its first operational use in a combat theater was in defense of the Port of Antwerp against V-1 flying bomb attacks during the Battle of the Bulge. In the Pacific War, batteries were deployed to safeguard United States Navy anchorages and forward bases like those on Okinawa and Iwo Jima. During the Korean War, the gun was used for air defense around key areas such as Incheon and Pusan Perimeter, though its role diminished with the advent of jet aircraft. It remained in the United States Army inventory until the early 1960s, when it was superseded by surface-to-air missile systems like the MIM-23 Hawk.

Variants

The primary variant was the **M1A1**, which featured a modified breech mechanism and an improved recoil system for more reliable operation. A proposed variant for the T28 Super Heavy Tank and the T95 Gun Motor Carriage was studied but never produced. Post-war, some guns were adapted for use in the Skysweeper project, an automatic anti-aircraft system, though this program was ultimately canceled.

Specifications

The 120 mm M1 had a barrel length of 276 inches (L/55). The complete system in firing position weighed approximately 64,000 pounds. It used a semi-automatic horizontal sliding-wedge breech. The gun carriage allowed for 360-degree traverse and an elevation range from -1 to +80 degrees. Its maximum rate of fire was 12 rounds per minute, though sustained fire was typically slower. The gun's maximum vertical range was 57,000 feet, with a maximum surface range of 19 miles.

Ammunition

The gun fired separate-loading ammunition, with a projectile and a brass case containing the propellant. Primary projectile types included the **M73** Armor-Piercing round for surface targets, the **M1** High-Explosive round, and the **M2** High-Explosive round with a mechanical time fuze for air bursts. The propellant charge was contained in a 775 mm long case, giving the round its designation 120 × 775 mm R.

Operators

The primary operator was the United States. A limited number of guns were supplied to the United Kingdom under Lend-Lease for the defense of Gibraltar and Malta. Post-war, a small number were transferred to Japan for the early Japan Ground Self-Defense Force and to South Korea following the Korean War. No other widespread exports were recorded.

Category:Anti-aircraft artillery of the United States Category:World War II anti-aircraft guns Category:120 mm artillery