M3 37 mm gun
Overview
 
The 37 mm Gun M3 was the first dedicated anti-tank gun fielded by United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 forces. Introduced in 1940, it became the standard anti-tank gun of the U.S. infantry
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 with its size enabling it to be pulled by a jeep
Willys MB
The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

. However, the continuing improvement of German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

s quickly rendered the 37 mm ineffective, and by 1943 it was being gradually replaced in the European
European Theater of Operations
The European Theater of Operations, United States Army was a United States Army formation which directed U.S. Army operations in parts of Europe from 1942 to 1945. It referred to Army Ground Forces, United States Army Air Forces, and Army Service Forces operations north of Italy and the...

 and Mediterranean
Mediterranean Theater of Operations
The Mediterranean Theater of Operations, United States Army was originally called North African Theater of Operations and is an American term for the conflict that took place between the Allies and Axis Powers in North Africa and Italy during World War II...

 theaters by the more powerful British-developed 57 mm Gun M1
Ordnance QF 6 pounder
The Ordnance Quick-Firing 6-pounder 7 cwt, or just 6 pounder, was a British 57 mm gun, their primary anti-tank gun during the middle of World War II, as well as the main armament for a number of armoured fighting vehicles...

.
Encyclopedia
The 37 mm Gun M3 was the first dedicated anti-tank gun fielded by United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 forces. Introduced in 1940, it became the standard anti-tank gun of the U.S. infantry
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 with its size enabling it to be pulled by a jeep
Willys MB
The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

. However, the continuing improvement of German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

s quickly rendered the 37 mm ineffective, and by 1943 it was being gradually replaced in the European
European Theater of Operations
The European Theater of Operations, United States Army was a United States Army formation which directed U.S. Army operations in parts of Europe from 1942 to 1945. It referred to Army Ground Forces, United States Army Air Forces, and Army Service Forces operations north of Italy and the...

 and Mediterranean
Mediterranean Theater of Operations
The Mediterranean Theater of Operations, United States Army was originally called North African Theater of Operations and is an American term for the conflict that took place between the Allies and Axis Powers in North Africa and Italy during World War II...

 theaters by the more powerful British-developed 57 mm Gun M1
Ordnance QF 6 pounder
The Ordnance Quick-Firing 6-pounder 7 cwt, or just 6 pounder, was a British 57 mm gun, their primary anti-tank gun during the middle of World War II, as well as the main armament for a number of armoured fighting vehicles...

. In the Pacific
Pacific Theater of Operations
The Pacific Theater of Operations was the World War II area of military activity in the Pacific Ocean and the countries bordering it, a geographic scope that reflected the operational and administrative command structures of the American forces during that period...

, where the Japanese tank threat was less significant, the M3 remained in service until the end of the war.

Like many other light anti-tank guns, the M3 was widely used in the infantry support
Infantry support gun
Infantry support guns are artillery weapons designed and used to increase fire power of infantry units they are intrinsic to, offering immediate tactical response to the needs of the unit's commanding officer. The designs are typically with short low velocity barrels, and light construction...

 role and as an anti-personnel weapon, firing high-explosive and canister
Canister shot
Canister shot is a kind of anti-personnel ammunition used in cannons. It was similar to the naval grapeshot, but fired smaller and more numerous balls, which did not have to punch through the wooden hull of a ship...

 rounds.

The M5 and M6 tank mounted variants were used in several models of armored vehicles most notably in the Light Tank M3/M5
Stuart tank
The M3 Stuart, formally Light Tank M3, was an American light tank of World War II and supplied to British and Commonwealth forces under lend-lease prior to the entry of the U.S. into the war—and used thereafter by U.S...

, the Medium Tank M3
M3 Lee
The Medium Tank M3 was an American tank used during World War II. In Britain the tank was called "General Lee", named after Confederate General Robert E. Lee, and the modified version built with a new turret was called the "General Grant", named after U.S. General Ulysses S. Grant.Design commenced...

 and the Light Armored Car M8
M8 Greyhound
The M8 Light Armored Car was a 6x6 armored car produced by the Ford Motor Company during World War II. It was used by the U.S. and British troops in Europe and the Far East until the end of the war. The vehicle was widely exported and as of 2006 still remains in service with some third world...

. In addition, the M3 in its original version was mated to a number of other self-propelled carriages.

Development history

In the mid-1930s, the United States Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 had yet to field a dedicated anti-tank artillery piece; anti-tank companies
Company (military unit)
A company is a military unit, typically consisting of 80–225 soldiers and usually commanded by a Captain, Major or Commandant. Most companies are formed of three to five platoons although the exact number may vary by country, unit type, and structure...

 of infantry regiment
Regiment
A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

s were armed with 0.5 in (12.7 mm) machine gun
Machine gun
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

s. Although there was some consideration had been given to replacing the machine guns with more a powerful anti-tank gun, the situation only began to change after the outbreak of the Spanish Civil War
Spanish Civil War
The Spanish Civil WarAlso known as The Crusade among Nationalists, the Fourth Carlist War among Carlists, and The Rebellion or Uprising among Republicans. was a major conflict fought in Spain from 17 July 1936 to 1 April 1939...

. Combat experience from Spain suggested that a light anti-tank gun, such as the German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 37 mm PaK 35/36, was capable of neutralizing the growing threat posed by tanks.

In January 1937, the Ordnance Committee recommended development of a such a weapon; two PaK 36 guns were acquired for study. As the projected main user of the weapon, the Infantry branch was chosen to oversee the work. They wanted a lightweight gun which could be moved around by the crew, so any ideas of using a larger caliber than that of the German gun were discarded. It should also be noted that 37 mm was a popular caliber of anti-tank guns in 1930s; other anti-tank guns of the same caliber included Swedish
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 Bofors gun
Bofors 37 mm
The Bofors 37 mm gun was an anti-tank gun designed by Swedish manufacturer Bofors in the early 1930s. Licensed copies were produced in a number of countries. The gun was used by some European armies during World War II, mainly at the early stage of the war.-Development history:The gun was...

, Czechoslovakia
Czechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

n vz. 34 and vz. 37, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese Type 94
Type 94 37 mm Anti-Tank Gun
The was an anti-tank gun developed by the Imperial Japanese Army, and used in combat during the Second Sino-Japanese War and World War II.-History and development:...

 and Type 1
Type 1 37 mm Anti-Tank Gun
The was an anti-tank gun developed by the Imperial Japanese Army, and used in combat during World War II.-History and development:After the Nomonhan Incident, the shortcomings of the Type 94 37 mm Anti-Tank Gun had become obvious, and the Imperial Japanese Army started the development of a new...

.

Development and testing continued until late 1938. Several variants of gun and carriage were proposed until on 15 December a combination of the T10 gun and T5 carriage was officially adopted as the 37 mm Gun M3 and Carriage M4. Although the weapon followed the concept of the PaK 36 and often referred to as a copy of it, the M3 differed significantly from the German design and used different ammunition.

The gun was manufactured by Watervliet Arsenal
Watervliet Arsenal
The Watervliet Arsenal is an arsenal of the United States Army located in Watervliet, New York, on the west bank of the Hudson River. It is the oldest continuously active arsenal in the United States, and today produces much of the artillery for the army, as well as gun tubes for cannons, mortars,...

 and the carriage by Rock Island Arsenal
Rock Island Arsenal
The Rock Island Arsenal comprises , located on Arsenal Island, originally known as Rock Island, on the Mississippi River between the cities of Davenport, Iowa, and Rock Island, Illinois. It lies within the state of Illinois. The island was originally established as a government site in 1816, with...

. The first pieces were delivered early in 1940, the production continued until 1943.
Production of М3, numbers of pieces.
Year 1940 1941 1942 1943 Total
Produced. 340 2,252 11,812 4,298 18,702


Some minor changes in the gun construction were introduced during production. The carriage received a modified shoulder guard and traverse controls (carriage M4A1, standardized on 29 January 1942). Although Ordnance requested an upgrade of all M4 carriages to M4A1, this process was not completed. Another change was a threaded barrel
Gun barrel
A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity....

 end to accept a big five-port muzzle brake
Muzzle brake
Muzzle brakes and recoil compensators are devices that are fitted to the muzzle of a firearm or cannon to redirect propellant gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire...

 (gun M3A1, adopted on 5 March 1942). According to some sources, the latter was intended to avoid kicking too much dust in front of the gun, which hindered aiming; however, the brake turned out to be a safety problem when firing canister ammunition and consequently the M3A1 went into combat without the muzzle brake. Other sources mention the muzzle brake was intended to soften a recoil and they say that it was dropped simply because additional recoil control measures were not really needed.

In an attempt to increase the armor penetration of the M3, several squeeze bore adapters (including the British Littlejohn adaptor
Littlejohn adaptor
The Littlejohn adaptor was a device that could be added to the British QF 2 pounder anti-tank gun. It was used to extend the service life of the 2-pounder during the Second World War by converting it to squeeze bore operation...

) were tested; none were adopted. Experiments with rocket launchers on the M4 carriage (e.g. 4.5 in (114.3 mm) rocket projector T3) did not produce anything practical either.

Description

The barrel was of one-piece forged construction, with uniform rifling (12 grooves, right-hand twist, one turn in 25 calibers). The breech end of the barrel was screwed into a breech ring. The breech mechanism was of vertical sliding-block type. The barrel was fitted with a hydrospring recoil system.

The carriage was of split trail type, with pneumatic tires. Mounted on the axle next to the wheels were the "wheel segments"; these were segment-shaped supports that could be lowered to provide more stability in the firing position or raised so that they would not impede movement of the gun.

The telescopic sight on the M6 and both elevation and traverse controls were located on the left side, so one gunner was able to aim the gun. The traverse gear had a release mechanism which allowed free movement of the barrel in case a quick traverse was needed.

Organization

US Army

Under organization from April 1942, each infantry battalion
Battalion
A battalion is a military unit of around 300–1,200 soldiers usually consisting of between two and seven companies and typically commanded by either a Lieutenant Colonel or a Colonel...

 had an anti-tank platoon
Platoon
A platoon is a military unit typically composed of two to four sections or squads and containing 16 to 50 soldiers. Platoons are organized into a company, which typically consists of three, four or five platoons. A platoon is typically the smallest military unit led by a commissioned officer—the...

 with four 37 mm guns (1/4 ton trucks
Willys MB
The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

, better known as jeeps, were authorized as prime movers) and each regiment
Regiment
A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

 an anti-tank company
Company (military unit)
A company is a military unit, typically consisting of 80–225 soldiers and usually commanded by a Captain, Major or Commandant. Most companies are formed of three to five platoons although the exact number may vary by country, unit type, and structure...

 with twelve (towed by 3/4 ton trucks
Dodge WC series
The Dodge WC series was a range of light military trucks produced by Dodge during World War II. The series included weapon carriers, telephone installation trucks, ambulances, reconnaissance vehicles, mobile workshops and command cars. They were replaced after the war by the Dodge M-series...

). Each of the four divisional artillery battalions possessed six anti-tank guns, combat engineering battalion nine pieces (towed by M2 halftrack
M2 Half Track Car
The M-2 Half Track was an armored vehicle used by the United States during World War II.-History:The half-track design had been evaluated by the US Ordnance department using Citroën-Kégresse vehicles...

s); in addition, divisional headquarters had four (towed by 3/4 ton trucks) and divisional maintenance company two.
Although an earlier organization included divisional anti-tank battalion (two companies of 37 mm guns and one company of 75 mm gun
Canon de 75 modèle 1897
The French 75mm field gun was a quick-firing field artillery piece adopted in March 1898. Its official French designation was: Matériel de 75mm Mle 1897. It was commonly known as the French 75, simply the 75 and Soixante-Quinze .The French 75 is widely regarded as the first modern artillery piece...

s), in December 1941 AT battalions were removed from divisional structure and reorganized as independent tank destroyer battalions; their towed guns were replaced with self-propelled ones as soon as the latter became available.

In 1942, the first airborne divisions were formed. According to their organizational structure of October 1942, an airborne division had 44 37 mm anti-tank guns: four in divisional artillery (AA/AT battery of parachute field artillery battalion), 24 in AA/AT battalion, and eight in each of two glider infantry
Glider infantry
Glider infantry was a type of airborne infantry in which soldiers and their equipment were inserted into enemy controlled territory via military glider rather than parachute...

 regiments; parachute infantry regiment did not have anti-tank guns. In practice, airborne divisions often had only one glider infantry regiment and therefore 36 guns.

37 mm guns were also issued to the infantry regiments of the only mountain division formed in the U.S.: the 10th Mountain Division.

Finally, U.S. armored division under organization from March 1942 possessed a total of 68 37 mm anti-tank guns. Of those, 37 belonged to armored infantry regiment (four in each company an one in regiment HQ); 27 to armored engineer battalion; three to divisional train and one to division HQ.

US Marine Corps

Under the D-series Tables of Organization (TO) from 1 July 1942, the role of AT weapons in Marine Corps
United States Marine Corps
The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...

 service was officially entrusted to 20 mm automatic guns, in regimental weapon company (three platoons) and battalion weapon company (one platoon). In practice, units used the World War I-era 37 mm M1916 for training. They were equipped with the M3 (four in each platoon) before being sent to the frontline. Additionally, a divisional special weapons battalion was equipped with self-propelled 37 mm GMC M6
M6 Fargo
The 37 mm Gun Motor Carriage M6 was a modified Dodge Light Truck mounting a light anti-tank gun. It was used by the US Army for infantry support and tank defense...

.

Under the E-series TO from 15 April 1943, self-propelled guns in the divisional special weapons battalion were replaced with eighteen 37 mm towed guns in three batteries of six; an infantry regiment had a weapons company with 12, in three platoons of four. The battalion-level AT guns were removed. In total, a division possessed 54 pieces. The F-series TO from 5 May 1944 removed the special weapons battalion from the divisional organization, resulting in a total of 36 guns per division. The subsequent G-series TO reduced regimental weapon companies to two platoons, meaning 24 pieces per division. Although the G-series TO was only adopted on 4 September 1945, in practice in some divisions this change was introduced early in 1945.

Other operators

The only major lend lease recipient of the M3 was the Chinese National Revolutionary Army
National Revolutionary Army
The National Revolutionary Army , pre-1928 sometimes shortened to 革命軍 or Revolutionary Army and between 1928-1947 as 國軍 or National Army was the Military Arm of the Kuomintang from 1925 until 1947, as well as the national army of the Republic of China during the KMT's period of party rule...

 (1,669 pieces). The gun was also supplied to Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

 (4), Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 (3), Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 (198), Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 (4), Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...

 (1), El Salvador
El Salvador
El Salvador or simply Salvador is the smallest and the most densely populated country in Central America. The country's capital city and largest city is San Salvador; Santa Ana and San Miguel are also important cultural and commercial centers in the country and in all of Central America...

 (9), France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 (130), United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 (78), USSR
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 (63) and other countries (100). Some nations still had it in service in the early 1970s.

Combat Service

The M3 saw action for the first time during the defense of the Philippines
Battle of the Philippines (1941-42)
The Philippines Campaign or the Battle of the Philippines was the invasion of the Philippines by Japan in 1941–1942 and the defense of the islands by Filipino and United States forces....

 in December 1941. It went on to become a factor in the Guadalcanal Campaign
Guadalcanal campaign
The Guadalcanal Campaign, also known as the Battle of Guadalcanal and codenamed Operation Watchtower by Allied forces, was a military campaign fought between August 7, 1942 and February 9, 1943 on and around the island of Guadalcanal in the Pacific theatre of World War II...

, where it was successfully employed against both Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese armor and infantry. Throughout the war it remained effective against Japanese vehicles, which were thinly armored and were rarely committed in large groups. The light weight of the gun made it easy to move through difficult terrain; for example, when attacked by Japanese tanks on Betio during the Battle of Tarawa
Battle of Tarawa
The Battle of Tarawa, code named Operation Galvanic, was a battle in the Pacific Theater of World War II, largely fought from November 20 to November 23, 1943. It was the first American offensive in the critical central Pacific region....

, Marines were able to heave the M3 over the 5 ft (1.5 m)-high seawall. While high explosive and canister ammunition
Canister shot
Canister shot is a kind of anti-personnel ammunition used in cannons. It was similar to the naval grapeshot, but fired smaller and more numerous balls, which did not have to punch through the wooden hull of a ship...

 proved useful in stopping Japanese infantry attacks, against enemy fortifications the M3 was only somewhat effective because of its small high-explosive projectile. Its overall effectiveness and ease of use meant the gun remained in service with the Marine Corps and with some Army units in the Pacific until the end of the war. Unhappy with the unusually low shield of the M3, some Marine Corps units extended it to provide better protection. These extensions sometimes had scalloped top edge, intended to improve camouflage. A standard kit was tested in 1945, but was never issued.

The experience of the M3 in the North African Campaign
North African campaign
During the Second World War, the North African Campaign took place in North Africa from 10 June 1940 to 13 May 1943. It included campaigns fought in the Libyan and Egyptian deserts and in Morocco and Algeria and Tunisia .The campaign was fought between the Allies and Axis powers, many of whom had...

 was completely different. The gun was not powerful enough to deal with late production German Panzer III
Panzer III
Panzer III was the common name of a medium tank that was developed in the 1930s by Germany and was used extensively in World War II. The official German designation was Panzerkampfwagen III translating as "armoured battle vehicle". It was intended to fight other armoured fighting vehicles and...

 and IV
Panzer IV
The Panzerkampfwagen IV , commonly known as the Panzer IV, was a medium tank developed in Nazi Germany in the late 1930s and used extensively during the Second World War. Its ordnance inventory designation was Sd.Kfz...

 tanks. After the nearly disastrous Battle of Kasserine Pass in February 1943, reports from some of the involved units mentioned 37 mm projectiles "bouncing off like marbles" from the turret and front armor of German medium tanks and proclaimed the gun "useless unless you have gun crews with the guts to stand and shoot from 100 yards". The Army was initially uncertain if these reports reflected the obsolescence of the weapon, or whether unrefined tactics and lack of experience were to blame. Yet on 26 May 1943 a new organization had the M3 replaced by the 57 mm Gun M1 (the U.S.-produced version of the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 6 pdr gun
Ordnance QF 6 pounder
The Ordnance Quick-Firing 6-pounder 7 cwt, or just 6 pounder, was a British 57 mm gun, their primary anti-tank gun during the middle of World War II, as well as the main armament for a number of armoured fighting vehicles...

),In service with the British Army
British Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 since 1942
with Dodge 1½ ton trucks as prime movers. Only by spring 1944 did the 57 mm gun reach the battlefield in large numbers.

Meanwhile, the Italian campaign
Italian Campaign (World War II)
The Italian Campaign of World War II was the name of Allied operations in and around Italy, from 1943 to the end of the war in Europe. Joint Allied Forces Headquarters AFHQ was operationally responsible for all Allied land forces in the Mediterranean theatre, and it planned and commanded the...

 was launched, and M3 guns saw action from the day of the Sicily landing
Allied invasion of Sicily
The Allied invasion of Sicily, codenamed Operation Husky, was a major World War II campaign, in which the Allies took Sicily from the Axis . It was a large scale amphibious and airborne operation, followed by six weeks of land combat. It launched the Italian Campaign.Husky began on the night of...

 on 10 July 1943. That day the 37 mm guns demonstrated once again both their effectiveness against pre-war tanks—when they helped to repel an attack by Italian Renault R 35s—and inability to cope with modern threats in a subsequent encounter with Tiger I
Tiger I
Tiger I is the common name of a German heavy tank developed in 1942 and used in World War II. The final official German designation was Panzerkampfwagen Tiger Ausf. E, often shortened to Tiger. It was an answer to the unexpectedly formidable Soviet armour encountered in the initial months of...

s from the Hermann Göring division
Fallschirm-Panzer Division 1 Hermann Göring
The Fallschirm-Panzer-Division 1. Hermann Göring was an élite German Luftwaffe armoured division. The HG saw action in North Africa, Sicily, Italy and on the Eastern front...

. The Italian theater had a lower priority for reequipment than Northwest Europe, and some M3s were still in use in Italy in late 1944.

By mid-1944, the M3 had fallen out of favor even with airborne troops, despite their strong preference for compact and lightweight weapon systems. The Airborne Command had rejected the 57 mm M1 in the summer of 1943 claiming its unfitness for airlifting and the Table of Organisation and Equipment (TO&E) of February 1944 still had airborne divisions keeping their 37 mm guns. Nevertheless, the 82nd
U.S. 82nd Airborne Division
The 82nd Airborne Division is an active airborne infantry division of the United States Army specializing in parachute landing operations. Based at Fort Bragg, North Carolina, the 82nd Airborne Division is the primary fighting arm of the XVIII Airborne Corps....

 and the 101st
101st Airborne Division
The 101st Airborne Division—the "Screaming Eagles"—is a U.S. Army modular light infantry division trained for air assault operations. During World War II, it was renowned for its role in Operation Overlord, the D-Day landings on 6 June 1944, in Normandy, France, Operation Market Garden, the...

, were reequipped with British-manufactured 6-pounder gun (57 mm) on carriage Mk III (designed to fit into the British Horsa glider
Airspeed Horsa
The Airspeed AS.51 Horsa was a British World War II troop-carrying glider built by Airspeed Limited and subcontractors and used for air assault by British and Allied armed forces...

) for the Normandy airdrops. This change was officially introduced in the TO&E of December 1944.

The M3 was phased out of U.S. service soon after the end of the war.

Variants

  • Test variants:
    • T3 - the first prototype.
    • T7 - a prototype with semi-automatic horizontal sliding block breech.
    • T8 - a prototype with Nordenfelt
      Thorsten Nordenfelt
      Thorsten Nordenfelt , was a Swedish inventor and industrialist.Nordenfelt was born in Örby outside Kinna, Sweden, the son of a colonel. The surname was and is often spelt Nordenfeldt, though Thorsten and his brothers always spelt it Nordenfelt, and the 1881 Census shows it as Nordenfelt...

       eccentric screw breech.
    • T10 - standardized as M3 (1938) - an adopted version, with manual vertical block breech.
  • Model variants
    • M3 towed version, manual breech.
      • M3A1 (1942) - version with threaded barrel end to accept a muzzle brake, which was never issued.
    • M5 (1939) - tank mounted variant with shorter barrel.
    • M6 (1940) - tank mounted variant with barrel of the original length and with semi-automatic breech.
  • Carriage variants:
    • T1, T1E1 - prototypes.
    • T5, standardized as M4 - first adopted version.
    • M4A1 (1942) - carriage with improved traverse controls.
    • In 1942, the Airborne Command requested a version with removable trails. A prototype was tested, but in 1943 the project was dropped as unnecessary.


At least in one case, Fifth Army Ordnance in Italy fitted the gun experimentally with fifteen 4.5 in (114.3 mm) aircraft rockets, in five clusters of three, mounted above the shield.

Variants of the M3 should not be confused with other 37 mm guns in the U.S. service. Those other pieces included M1916 infantry gun of French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 design (these were later used extensively as subcaliber devices for heavy artillery.), M1 antiaircraft autocannon, M4/M9/M10
M4 cannon
The 37 mm Automatic Gun, M4, known as the T9 during development, was a 37 mm autocannon designed by John Browning and used in the Bell P-39 Airacobra and P-63 Kingcobra fighters, as well as experimentally on other designs. It provided interceptors with a weapon that could shoot down any...

 aircraft-mounted autocannons, M12/M13/M14/M15 subcaliber guns.

Self-propelled mounts

Two tank gun variants were developed based on the barrel of the M3. The first, initially designated M3A1 but renamed M5 on 13 October 1939, was shortened by 5.1 in (129.5 mm) to avoid damage to the tube in wooded areas. Later, a variant with a semi-automatic breech (with empty cartridge ejection) was developed. This variant—initially designated M5E1, adopted as M6 on 14 November 1940—received a full length barrel. The tubes were interchangeable, but replacing M5 with M6 and vice versa would result in an unbalanced mount and was therefore prohibited. These guns were mounted on several models of tanks and other armored vehicles:
  • Light Tank M2A4
    M2 Light Tank
    The Light Tank M2 was an American pre-World War II light tank that saw combat with the US Marine Corps 1st Tank Battalion on Guadalcanal in 1942, during World War II. Its service with the 1st Tank Battalion during the Pacific War was its only U.S...

    : M5 in mount M20. The recoil mechanism, protruding beyond the gun mask, had to be protected by an armored casing.
  • Light Tank M3
    Stuart tank
    The M3 Stuart, formally Light Tank M3, was an American light tank of World War II and supplied to British and Commonwealth forces under lend-lease prior to the entry of the U.S. into the war—and used thereafter by U.S...

    : M5 in mount M22, in late production vehicles M6 in mount M23. These mounts were fitted with more compact recoil mechanism, eliminating the need for the protective casing.
  • Light Tank M3A1, M5
    Stuart tank
    The M3 Stuart, formally Light Tank M3, was an American light tank of World War II and supplied to British and Commonwealth forces under lend-lease prior to the entry of the U.S. into the war—and used thereafter by U.S...

    : M6 in mount M23.
  • Light Tank M3A3, M5A1
    Stuart tank
    The M3 Stuart, formally Light Tank M3, was an American light tank of World War II and supplied to British and Commonwealth forces under lend-lease prior to the entry of the U.S. into the war—and used thereafter by U.S...

    : M6 in mount M44.
  • Light Tank (Airborne) M22
    M22 Locust
    The Light Tank M22 or Locust was an American-designed airmobile light tank which was produced during World War II. The Locust began development in 1941 after the British War Office requested that the American government design a purpose-built airborne light tank which could be transported by...

    : M6 in mount M53.
  • M3 series medium tanks (as a secondary weapon): M5 or M6 in mount M24.
  • Heavy Tank M6
    M6 Heavy Tank
    The Heavy Tank M6 was an American heavy tank designed during World War II. The tank was produced in small numbers and never saw combat.-History and description:...

     (as a secondary weapon): M6 in mount T49.
  • LVT(A)-1 "amtank"
    Landing Vehicle Tracked
    The Landing Vehicle Tracked was a class of amphibious vehicles introduced by the United States Navy, Marine Corps and Army during World War II. Originally intended solely as cargo carriers for ship to shore operations, they rapidly evolved into assault troop and fire support vehicles as well...

    : M6 in mount M44.
  • 37 mm Gun Motor Carriage T22 - eventually Light Armored Car M8
    M8 Greyhound
    The M8 Light Armored Car was a 6x6 armored car produced by the Ford Motor Company during World War II. It was used by the U.S. and British troops in Europe and the Far East until the end of the war. The vehicle was widely exported and as of 2006 still remains in service with some third world...

    : M6 in mount M23A1; the competing designs 37 mm Gun Motor Carriage T43 / Light Armored Car T21 and 37 mm Gun Motor Carriage T23 / Light Armored Car T23 mounted the same weapon.
  • Armored Car T13.
  • Armored Car T17
    T17 Armored Car
    The T17 and the T17E1 were American armored cars produced during the Second World War. They did not see service with frontline US forces but the latter was supplied via the United Kingdom to British and Commonwealth forces during the war and received the service name Staghound...

    : M6 in mount M24.
  • Armored Car T17E1
    T17 Armored Car
    The T17 and the T17E1 were American armored cars produced during the Second World War. They did not see service with frontline US forces but the latter was supplied via the United Kingdom to British and Commonwealth forces during the war and received the service name Staghound...

     in the "Staghound Mk I" configuration: M6 in mount M24A1.
  • The first pilot of the Armored Car T18
    T18 Boarhound
    The T18 Boarhound was an American heavy armoured car produced in small numbers for the British Army during the Second World War.-History:In July 1941 the US Army Ordnance Corps issued specifications for a heavy armored car to be built for supply to the British...

    : M6. The production variant T18E2 received the 57mm M1.
  • Armored Car T19: M6 in mount M23A1.
  • Armored Car T27
    T27 Armored Car
    The T27 Armored Car was a prototype armored car developed for the US Army in 1944 by the Studebaker Corporation. The T27 was an eight wheeled vehicle, with the 1st, 2nd and 4th pairs of wheels being powered. With a crew of four, the T27 was armed with two .30 caliber machine guns and a 37 mm...

    : M6 in mount M23A1 modified.
  • Armored Car T28 / M38
    M38 Wolfhound
    The M38 Wolfhound was a 6x6 US armored car produced in 1944 by the Chevrolet division of the General Motors. It was designed as a replacement for the M8 Greyhound series, but the end of the war in 1945 led to the cancellation of the project after the completion of a handful of prototype...

    : M6 in mount M23A2.
  • British
    United Kingdom
    The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

     Humber Armoured Car Mk IV
    Humber Armoured Car
    The Humber Armoured Car was one of the most widely produced British armoured cars of the Second World War. It supplemented the Humber Light Reconnaissance Car and remained in service until the end of the war.-Development:...

    : M6.


Versions of the gun in turret mounts were also used in the Medium Tank T5 Phase III (T3 barrel, mount T1), in the Medium Tank M2 / M2A1
M2 Medium Tank
The Medium Tank M2 was a United States Army tank that was first produced in 1939 by the Rock Island Arsenal, just prior to the commencement of the war in Europe. Production was 18 M2 tanks, and 94 slightly improved M2A1 tanks, for a total figure of 112...

 (M3 barrel, M2A1: mount M19), and in the 37mm Gun Motor Carriage T42 (mount M22).
In addition, M3 on different pedestal mounts was mated to a number of other vehicles resulting in an assortment of 37 mm gun motor carriages. Only the M6
M6 Fargo
The 37 mm Gun Motor Carriage M6 was a modified Dodge Light Truck mounting a light anti-tank gun. It was used by the US Army for infantry support and tank defense...

 reached mass production.
  • 37 mm Gun Motor Carriage T2 (Bantam jeep
    Willys MB
    The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

    ).
  • 37 mm Gun Motor Carriage T8 (Ford 4x4 "Swamp Buggy").
  • 37 mm Gun Motor Carriage T13, T14 (Willys 6x6 "Super Jeep").
  • 37 mm Gun Motor Carriage T21 / M4 / M6
    M6 Fargo
    The 37 mm Gun Motor Carriage M6 was a modified Dodge Light Truck mounting a light anti-tank gun. It was used by the US Army for infantry support and tank defense...

     (Fargo 3/4 ton 4x4 truck).
  • 37 mm Gun Motor Carriage T33 (Ford 3/4 ton 4x4 cargo carrier).
  • M3A1E3 Scout Car
    M3 Scout Car
    The M3 Scout Car was an armored car in U.S. service during World War II. It was also known as the White Scout Car, after its manufacturer, the White Motor Company. It was used in various roles including patrol, scouting, command vehicle, ambulance and gun tractor.-History:Design of the vehicle...

    .
  • The gun was sometimes mounted on M2 Halftrack
    M2 Half Track Car
    The M-2 Half Track was an armored vehicle used by the United States during World War II.-History:The half-track design had been evaluated by the US Ordnance department using Citroën-Kégresse vehicles...

    , M29 Weasel
    M29 Weasel
    The M29 Weasel was a World War II tracked vehicle, built by Studebaker, designed for operation in snow.-Design and development:The idea for the Weasel came from the work of British inventor Geoffrey Pyke in support of his proposals to attack Axis forces and industrial installations in Norway...

     and on the 1/4 ton Willys MB / Ford GPW jeep
    Willys MB
    The Willys MB US Army Jeep and the Ford GPW, were manufactured from 1941 to 1945. These small four-wheel drive utility vehicles are considered the iconic World War II Jeep, and inspired many similar light utility vehicles. Over the years, the World War II Jeep later evolved into the "CJ" civilian...

     (see photo on the right).


On several occasions, the M3 was mounted on PT boat
PT boat
PT Boats were a variety of motor torpedo boat , a small, fast vessel used by the United States Navy in World War II to attack larger surface ships. The PT boat squadrons were nicknamed "the mosquito fleet". The Japanese called them "Devil Boats".The original pre–World War I torpedo boats were...

s to increase their firepower. One of these boats was John F. Kennedy
John F. Kennedy
John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the 35th President of the United States, serving from 1961 until his assassination in 1963....

's PT-109
Motor Torpedo Boat PT-109
PT-109 was a PT boat last commanded by Lieutenant, junior grade John F. Kennedy in the Pacific Theater during World War II...

. The gun with its wheels removed was mounted on wooden planks nailed to the deck.

Ammunition

The M3 utilized fixed ammunition. Projectiles were fitted with a 37x223R cartridge case, designated Cartridge Case M16. Available projectiles included armor piercing, high explosive and canister.
Available ammunition
Type Model Weight, kg (round/projectile) Filler Muzzle velocity, m/s (M3&M6/M5)
AP-T
Armor-piercing shot and shell
An armor-piercing shell is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions...

AP M74 Shot 1.51 / 0.87 - 884 / 870
APCBC-T APC M51 Shot 1.58 / 0.87 - 884 / 870
HE HE M63 Shell 1.42 / 0.73 TNT, 39 g 792 / 782
HE HE Mk II Shell 1.23 / 0.56 TNT, 27 g
Canister
Canister shot
Canister shot is a kind of anti-personnel ammunition used in cannons. It was similar to the naval grapeshot, but fired smaller and more numerous balls, which did not have to punch through the wooden hull of a ship...

Canister M2 1.58 / 0.88 122 steel balls 762 / 752
Target practice with tracer TP M51 Shot 1.54 / 0.87 -
Drill (simulates APC M51) Drill Cartridge M13 1.45 / 0.87 - -
Drill (simulates HE M63) Drill Cartridge T5 1.45 / 0.73 - -
Blank Blank Cartridge 10-gage
Gauge (bore diameter)
The gauge of a firearm is a unit of measurement used to express the diameter of the barrel. Gauge is determined from the weight of a solid sphere of lead that will fit the bore of the firearm, and is expressed as the multiplicative inverse of the sphere's weight as a fraction of a pound . Thus...

with adapter M2
0.93 / - - -

 

Armor penetration table, M3 or M6
Ammunition \ Distance, yd / m 500 / 457 1,000 / 914 1,500 / 1,371 2,000 / 1,828
AP M74 Shot (meet angle 0°) 36
AP M74 Shot (meet angle 20°) 25
APC M51 Shot (meet angle 0°) 61
APC M51 Shot (meet angle 20°) 53
APC M51 Shot (meet angle 30°, homogeneous armor) 53 46 40 35
APC M51 Shot (meet angle 30°, face-hardened armor) 46 40 38 33
Different methods of armor penetration measurement were used in different countries / periods. Therefore, direct comparison is often impossible.


Armor penetration of the M5 was about 3 mm less at all ranges.

External links

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