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M1 8 in (203 mm) howitzer
M115 8 in (203 mm) howitzer

The M115 8 in (203 mm) howitzer, which was replaced by the M110 self-propelled howitzer, is a towed weapon developed prior to World War II as a heavy artillery weapon. The weapon uses NATO standard 203mm ammunition, and was used during World War II, in Korea, and in Viet Nam. In NATO service their prime mission was to fire nuclear rounds which have since been phased out of service.

The first American attempt to develop a 203mm gun had failed in the early 1920's due to budgetary constraints. During World War I the US Army had determined that an 8" field gun would be desirable, in 1919 a specification for this weapon was founded but all work was suspended in 1924.

The project was relaunched in 1939 as an answer to the German 17cm K18. Intended to be used in conjunction with the 240mm M1 howitzer, it shared with it many components, among them the mount and the breech. The 8" Howitzer was the "partner piece" to the American 155mm gun, in that both used the same carriage to mount different barrels for different roles.

Tests of the prototype T3 howitzer began at Aberdeen Proving Ground in 1939 and the howitzer entered service as the 8 in Howitzer M1. The prototype T2 took a long time before being standardized as the M1 in January of 1944. The inner surface of the barrel was subjected to a high erosion by its shells, which increased dispersion and was detrimental to accuracy. Although it could fire further and launched a heavier shell than its German counterpart, production numbers remained limited and it was usually confined to training duties. The wheels are removed from the carriage when in use and it takes some time to prepare the M1 for travel or to place into a new firing position. the carriage is designed for high speed travel.

The original WW2 M1 series (which became the M2 with some manufacturing improvements) put a 95lb/42kg HE shell to 25,000 yards/23km while the 8" - also designated M1 and later M2 - fired its heavier 203mm calibre 200lb/90kg shell to 18,000 yards/17km. Both guns were the mainstay of American and allied heavy artillery units and served for many years post-war with US forces as well as being widely distributed to America's allies.

After the Second World War the complete weapon was redesignated the Howitzer, Heavy, Towed: 8 in: M115. They were redesignated as M115 for the 8" and this gun was used in its original 25 calibre format in the early model M110 series self-propelled guns. As such it served for many years, with the M115 in towed form being still in service in the 1990s which shows what a solid and reliable gun it was. It was also capable of firing nuclear rounds. Its 155mm partner was also used for many years, under its new title of M59. The same carriage was also adopted by the British Army to mount the 7.2" Howitzer Mk 6.

Variants of the M110 with a longer barrel include the M110A1 (no muzzle brake) and the M110A2 (fitted with muzzle brake). In most countries the M115 and the M110 have been phased out of service due to short range. The carriage of the 8 in howitzer is also used to mount the 155 mm Gun M1 (Long Tom), which is still in use with some armies.

The carriage consists of equilibrator assemblies, elevating and traversing mechanisms, two single-wheel, single-axle heavy limber, two-axle bogie with eight tyres and two trails. Four spades, carried on the trails, are used to emplace the weapon. In recent years some armies have towed the weapon without the limber.

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