US Army Anti Tank Gun
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- Last updated: 23/08/2021
When America entered WWII in December 1941, the anti-tank gun the army had taken into service only two years earlier as the 37mm calibre M3, was already obsolete. It was not a question of poor weapon design, but rather the development of the heavier armour fitted to German tanks, which defeated the calibre of the ammunition being used. To be fair, in the immediate pre-war years, no one could have predicted how powerful tanks would become and few armies had anti-tank guns with a calibre heavier than 37mm, which included the German PaK 36. However, not all was lost when it was discovered that it could defeat Japanese tanks, which were notorious for having only light armour, which the 37mm ammunition could defeat. The gun was also put into a secondary role as a means to ‘snipe’ against Japanese pillboxes and machine gun sites using the HE ammunition. The first major combat commitment for the US Army was the invasion of North Africa, ‘Operation Torch’ in November 1941, and it was during the campaign which followed that the M3 anti-tank gun, or rather the ammunition, showed a lack of ‘punch’ when it failed against German tanks.
By the time of the operation the gun had already undergone some modifications, which included the fitting of a muzzle brake to try to reduce the recoil, leading to it being designated the M3A1. However, it was often removed, something which comes through in wartime photographs. A new two-wheeled carriage was also designed for the gun, this being the M4A1, fitted with a clutch on the traverse mechanism, allowing the gun to be freely swung by hand. Despite these changes, the decision was taken to remove it from the theatre of operations and during the European campaign in 1944 it had a very limited role.
The length of the gun barrel was 6ft-10, but taking into account the legs of the split trail carriage meant that the overall length measured in at 12ft-10. The width was approximately 5ft-3 and the height to the top of the gun shield was around 3ft-2. The total weight of the gun in action was 912lbs.
The M3A1 was operated by a crew of four to six men and the breech mechanism was a handoperated, vertical sliding blocktype with percussion firing. The barrel could be elevated between -10 and +15° with a 30° arc of traverse. Its light weight meant it could be towed by a Jeep or a Dodge ‘Weapons Carrier’, either of which could carry the crew and ammunition ready for use.
The maximum range given, very optimistically, was around 1,300 yards, while the maximum effective range was given, more realistically, as 500 yards. Several different types of fixed ammunition were developed for the M3A1 gun, measuring 37mm in calibre and 223mm in length, which included training rounds, however, only five main types were used in action against targets. The first were anti-tank rounds, which included the M-74 Armour-Piercing-Tracer (AP-T) and the M-51 Armour-Piercing Cap Ballistic Capped-Tracer (APCBC-T). Both of them weighed 3.3lbs complete with the projectile weighing 1.9lbs. They reached a muzzle velocity of 2,900 FPS with the M-74 penetrating up to 53mm of armour at 500 yards and the M-51 defeating 61mm at the same range. The performance dropped off considerably at longer ranges, but overall remained comparable to other guns of a similar calibre.
The high explosive (HE) ammo included the M-63 and the MkII shells, which weighed 3.1lbs and 2.7lbs respectively as complete rounds. These could be used against soft targets such as trucks and machine-gun positions. The projectile of the M-63 weighed 1.6lbs and contained just over 1oz of TNT, while the MkII one came in at 1.2lbs and housed approximately 1oz of TNT. Lastly, the canister anti-personnel weighed 3.4lbs and fired a 1.9lb projectile filled with 122 steel balls. Delivered at a muzzle velocity of 2,500 FPS, like a shotgun shell, the pattern of the steel balls spread out to rip through the dense jungle vegetation on the Pacific islands, such as Iwo Jima, Saipan and Tarawa. The effective range was 250 yards and at close range would have been devastating.
Versions of the 37mm calibre gun were developed as armament for armoured cars and light tanks, such as the M-3 ‘Honey’ and M-5 ‘Stuart’. The M3A1 could be used with extemporised mounts to fire from light vehicles, including the Jeep and M-3 White halftracks. A small number of the towed versions were supplied to Britain and the Soviet Union.
After the war, several countries including Nicaragua, Bolivia and France continued the use the gun throughout the 1950s. A total of 18,702 M3A1 guns were built by Watervliet Arsenal, with carriages being produced by the Rock Island Arsenal.
Like all weapons, the M3A1 and its ammunition types have become of interest to collectors and re-enactors for use in static displays. Original examples of the gun, which have been renovated or require attention are available through specialist websites. The different types of ammunition with identification colours are also available. It amounts to the old words of wisdom to first look around at what is being offered. If owning an original example is outside your budget, then there is always a replica alternative, and several companies are making the M3A1 and other similar weapons. Made from sheet steel, these are very passable copies, which can fit into a static display or even a liveaction battle re-enactment.
Some vehicle owners have an example of the gun, either replica or real, which they attach to their Jeeps or Dodge WC-51 ‘Weapons Carrier’ and reproduce an authentic image straight from WWII. The effect gives modellers a great photo opportunity and weapon enthusiasts something to remember, also. When seen as part of a convoy on a ‘road run’, the combination is like looking back into the past. Collectors who specialise in ammunition can purchase examples of the different types either from online traders or at a militaria fair, where dealers will have items. The chance of picking up training manuals or other documentation connected with the gun is always something to look for.
Because of its history, the M3A1 gun is a versatile piece of kit that can be included in various displays to depict different theatres of war, including North Africa, the Pacific with the US Marines, Sicily 1943 or Europe. It can also be used by groups depicting the WWII Russian army or even the British army. Replica versions can be modified to mount on vehicles such as the M3 half-track, to show it in another role. For groups depicting post-war conflicts, for example, the French army at Dien Bien Phu during the 1950s Indo-China War, the gun can fit in with such a display.
There are some very good replicas available, along with ammunition, which might just tempt some groups to consider including an M3A1 anti-tank gun in their displays. It is a possibility, but in the meantime, we will just have to wait and see.