37mm Gun M3

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37mm Gun M3 on Carriage M4
Anti-tank gun crews training, Fort Benning.
Type	anti-tank gun
Place of origin	United States
Service history
Wars	World War II
Production history
Designed	1938
Manufacturer	Gun: Watervliet Arsenal, Carriage: Rock Island Arsenal
Produced	1940-1943
Number built	18,702
Specifications
Weight	413.68 kg
Length	3.92 m
Barrel length	53.5 calibers
Width	1.61 m
Height	0.96 m
Crew	4
Caliber	37 mm
Breech	vertical block
Recoil	hydrospring
Carriage	split trail
Elevation	-10° to +15°
Traverse:	60°
Rate of fire	up to 25 rounds per minute
Maximum range	11,790 m
Sights	telescopic

The 37mm Gun M3 was the first dedicated anti-tank gun fielded by the US Army. Introduced in 1940, it remained the standard anti-tank gun of the US infantry for most of World War II.

[edit] Development history

Manhandling a gun into position during a training at Fort Benning. Note the raised segments mounted on the axle next to the wheels; they could be lowered to provide additional support for the gun in firing position.

Loading the gun (crew training, Fort Benning).

Aiming the gun (crew training, Fort Benning).

US 37mm gun crew in combat at Saipan, 1944. The shield is fitted with some kind of extension plate.

37mm GMC M6 with improvised machine gun mount.

Soldiers of the US 3rd Infantry (the "Old Guard") on maneuvers as part of the defense of St Johns, Newfoundland, 1942.

Light Tank M2A4 armed with the M5 gun, 1941. Note the armored casing protecting recoil mechanisms. For M3 series light tanks a more compact recoil system was developed, eliminating the need for the casing.

In late 1930s the US Army had yet to field a dedicated anti-tank gun. Anti-tank companies of infantry regiments were armed with .50-cal machine guns, which were considered capable enough against most tanks of the 1920s and 1930s. Although there were some considerations of replacing the MGs with more powerful weapon, only in January 1937, inspired by reports about succesful use of anti-tank guns in Spanish Civil War, the Ordnance Committee recommended development of a such a weapon; a German 3,7 cm PaK 35/36 was acquired for evaluation. The Infantry branch was chosen to oversee the work as a future primary user of the weapon. While some Ordnance officers considered larger caliber, the Infantry insisted on 37mm since it wanted lightweight gun which could be moved around by a four man crew. In August 1938 the War Department notified the Ordnance that there will be no funding anytime soon for a larger gun.^[1]

Development and testing continued until late 1938. Several variants of gun and carriage were proposed until on 15 December a combination of T10 gun and T5 cariage was officially adopted as 37mm Gun M3 and Carriage M4.^[1] Although patterned after PaK 36 and often referred to as a copy of it^[2], the M3 differed from the German design in many aspects.

The gun was manufactured by Watervliet Arsenal and the carriage by Rock Island Arsenal. First pieces were deliviered early in 1940.^[1] The production continued until 1943.

Some minor changes in the gun construction were introduced during the production period. The carriage received improved traverse controls (carriage M4A1, standardized on 29 January 1942); although Ordnance requested upgrade of all M4 carriages to M4A1, the process wasn't completed.^[1] Other change was threaded barrel end to accept a big five-port muzzle brake (gun M3A1, adopted on 5 March 1942). According to Zaloga,^[1] the latter was intended to avoid kicking too much dust under dry ground conditions; it turned out to be a safety problem when used with canister ammunition and consequently never saw combat. Other sources mention the muzzle break as intended to soften a recoil and say that it was dropped simply because the gun didn't really need additional recoil control measures.^[4][5]

A number of tank gun variants were developed based on the barrel of the M3. These were used in several models of American tanks (most notably the M3/M5 light tanks and the M3 medium tank) and armored cars (most notably the M8). In addition, M3s were mated to a number of other vehicles resulting in an assortment of 37mm gun motor carriages. See the Variants section for details.

[edit] Organization and employment

Under the Table of Organization and Equipment (TO&E) active in 1941, each infantry battalion had an anti-tank platoon with three 37mm guns and each regiment an anti-tank company with nine, totaling 18 pieces per regiment. The TO&E named 3/4 ton trucks as prime movers, but many units received the 1/4 ton truck (better known as the jeep) instead. Two anti-tank companies were also supposed to be a part of the divisional anti-tank battalion (along with eight 75mm guns), but in December 1941 these battalions were reorganized as independent tank destroyer battalions and eventually opted for self-propelled anti-tank guns.^[6] An airborne division had 36 37mm anti-tank guns under TO&E of October 1942: four in divisional artillery, eight in glider infantry regiment, 24 in AA/AT battalion.^[7]

The M3 saw action for the first time during the defense of the Philippines in December 1941.^[6] Throughout the war it remained effective against Japanese vehicles (which were thinly armored and, moreover, were rarely committed in large groups) and its weight allowed to manhandle it with relative ease (e.g. when attacked by Japanese tanks on Betio, marines were able to manually heave the M3 over the five-foot-high seawall^[8]). Because of those factors, the gun remained in service with the Marine Corps until the end of the war, being employed in both anti-tank and infantry support roles. Some Army units in the Pacific also used the gun until the end of the hostilities.^[6] Unhappy with an unusually low shield of the M3, some Marine Corps units extended them to provide better protection. A standard kit was tested in 1945 but was never issued.^[9]

The experience of the North African Campaign was completely different. The gun was soon found out to be not powerful enough to deal with German Panzer III and Panzer IV. After the nearly disastrous Battle of Kasserine Pass in February 1943, US Army reports mentioned 37mm projectiles "bouncing off like marbles" from 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 Ground Force, however, was still uncertain whether the gun was inadequate or was simply incorrectly used; so the TO&E from March left the M3 in place. Only on 26 May 1943 another new TO&E had the M3 replaced by the 57mm Gun M1 (the US-produced version of the British QF 6 pounder), with Dodge 1 1/2 ton trucks as prime movers. But only by spring 1944 did the 57mm gun reach battlefield in large numbers.^[6] In Italy, some M3s were still in use late in 1944.^[10]

Although the TO&E of February 1944 still had airborne divisions keep their 37mm guns, before the Normandy airdrops the two divisions involved - the 82nd and the 101st - were reequipped with a lightweight version of the 6 pounder.^[7]

The only major lend lease recipient of the M3 was the Chinese Kuomintang Army (1,669 pieces). The gun was also supplied to Bolivia (4), Canada (3), Chile (198), Colombia (4), Cuba (1), El Salvador (9), France (130), Great Britain (78), USSR (63) and other countries (100).^[11]

[edit] Variants

• Gun variants:
  • T3 - the first prototype.^[1]
  • T7 - a prototype with semi-automatic horizontal sliding block breech.^[4]
  • T8 - a prototype with Nordenfelt eccentric screw breech.^[4]
  • T10, standardized as M3 - an adopted version, with manual vertical block breech.^[1][4]
  • M3A1 (1942) - version with threaded barrel end to accept a muzzle break, which was never issued.^[1]
• Carriage variants:
  • T1, T1E1 - prototypes.^[1]
  • T5, standardized as M4 - first adopted version.^[1]
  • M4A1 (1942) - carriage with improved traverse controls.^[1]
  • In 1942 the Airborne Command requested a version with removable trails. A prototype was tested, but in 1943 the project was dropped as unnecessary.^[1]
• Self-propelled mounts:
  • 37mm Gun Motor Carriage T2, T2E1 (Jeep).^[5]
  • 37mm Gun Motor Carriage T8, T33, T44 (Ford swamp buggy).^[5]
  • 37mm Gun Motor Carriage T13 (6x6 truck).^[5]
  • 37mm Gun Motor Carriage T21, M4, M6 (Dodge 3/4 ton 4x4 truck).^[5]
  • M29 Weasel.^[5]
• Tank gun variants:
  • M3A1, redesignated M5 - tank gun with barrel shortened by 5.1 inch (3.5 calibers).^[12] Was used in:
    • Light Tank M2A4.^[12]
    • Most of Light Tank M3.^[12]
    • Some early production M3 series medium tanks (as a secondary weapon).^[13]
  • M5E1, redesignated M6 - tank gun with full-length barrel and semiautomatic breech mechanism (with empty cartrige ejection).^[12] Was used in:
    • M3/M5 series light tanks starting with late production M3.^[12]
    • Most of the M3 series medium tanks (as a secondary weapon).^[13]
    • Light Tank (Airborne) M22.^[14]
    • Heavy Tank M6 (as a secondary weapon).^[15]
    • LVT(A)-1 "amtank".^[16]
    • Light Armored Car T22 / M8 and the competing designs T21 and T23.^[5]
    • Armored Car T17 / T17E1.
  • Versions of the gun were used in the experimental Medium Tank T5 Phase III (T3 barrel)^[17] and in the Medium Tank M2 (M3 barrel).^[18]

In attempt to increase the armor penetration of the M3 several squeeze bore adaptors (including the British Littlejohn adaptor) were tested; none were adopted. Experiments with rocket launchers on the M4 carriage (e.g. 4.5in rocket projector T3) also didn't produce anything practical.^[1]

[edit] Ammunition

[edit] Notes

[edit] References

Wikimedia Commons has media related to:

M3 37 mm gun

• Zaloga, Steven J. and Delf, Brian - US Anti-tank Artillery 1941-45, Osprey Publishing, 2005 (New Vanguard 107), ISBN 1-84176-690-9.
• Hogg, Ian V. - Allied Artillery of World War Two - Crowood Press, Ramsbury, 1998, ISBN 1-86126-165-9.
• Chamberlain, Peter and Gander, Terry - Anti-Tank Weapons, Arco Publishing Company, New York, 1974 (WWII Fact Files), ISBN 0-66803-505-6.
• Rottman, Gordon and Chapell, Mike - The US Marine Corps 1941-45, Osprey Publishing 1995 (Elite 59), ISBN 1-85532-497-0.
• Hunnicutt, R. P. - Stuart: A History of the American Light Tank., Presidio Press 1992, ISBN 0-89141-462-2.
• Hunnicutt, R. P. - Sherman: A History of the American Medium Tank., Presidio Press 1994, ISBN 0-89141-080-5.
• Hunnicutt, R. P. - Firepower: A History of the American Heavy Tank., Presidio Press 1988, ISBN 0-89141-304-9.
• USA Guns 37mm calibre: penetration table at "Guns vs Armour 1939 to 1945" website.