155mm Gun M1/ M1A1/ M2

The 155mm Gun M1/ M1A1/ M2 ‘Long Tom’ was an improved version of a French gun used by the US Army during the First World War, and was one of the most important US artillery pieces of the Second World War.

During the First World War the US Army was given a number of different types of British and French artillery pieces, including the excellent 155mm Grand Puissance Filloux (produced in the US as the 155mm Gun M1918). In the interwar period the US Army attempted to produce an improved version of this gun, a rather haphazard process that didn’t actually produce a final product until the late 1930s.

US 155mm Gun M1 (Long Tom) on Rendova Island

Serious work began with the 155mm Gun T4 on Carriage T2 of 1929. The main aim of the programme was to improve the range of the weapon from the 20,000 yards of the M1918 to around 25,000 yards. The new gun was standardized as the 155mm Gun M1 in 1938, and entered serial production after the outbreak of war in Europe in 1939.

The resulting 155mm Gun M1 used the barrel from the French original, with an Asbury breech mechanism that helped increase the rate of fire. The most important improvement in the new gun was the Carriage M1, which was a split trail carriage that allowed the gun to be elevated to 65 degrees and traversed by 60 degrees. The carriage had four wheels mounted on each side at the front. In combat the wheels were raised allowing the firing platform to rest on the ground. This gave the new 155mm gun a very stable firing platform and helped to improve its accuracy. The same Carriage M1 was also used with the US 8in Howitzer M1 and the British 7.2in Howitzer Mk V and much improved 7.2in Howitzer Mk 6.

The barrel was balanced by two hydro-pneumatic cylinders which were mounted diagonally along the side of the barrel, mounted to a pair of horns just above and in front of the breech, and to the front of the cradle below the barrel. The recoil system automatically responded to the gun’s elevation. The barrel could be retracted into a travelling position, when it was supported by an A-Frame attached to the trails.

French crew loading US 155mm Gun, Italy, 1944

Two modified versions of the gun entered production - the M1A1 and M2. The M1A1 eliminated the breech-ring bushing (which had carried the breech threads), and instead had the threads cut directly onto the breech ring. The M1A1 was standardized on 12 June 1941, after only twenty M1s had been completed. The M1A1 was the main production version. The M2, which had a modified breech ring, was standardized on 15 March 1945.

A number of experimental versions were produced. The M1A1E1 had chromium plating on the bore. The M1A1E3 used liquid injection cooling in an attempt to reduce wear.

A variety of carriages and limbers were produced for the 155mm gun. The Carriage M1A1 was the original T2 carriage updated for service use. The M5 heavy carriage limber was designed to make it quicker to emplace the gun and was standardised in March 1944.

The 155m Gun could also be used with a special ‘Kelly Mount’ which gave it 360 degrees of traverse. This involved a central pivot that went under the middle of the carriage, and a circular rail that surrounded the position. The end of the trails were given wheels that rode on the track, allowing the entire gun to be moved around fairly easily.

The 155mm Gun became one of the standard heavy guns in the US arsenal, and was also issued to many of her allies, including Britain. The British used the gun from D-Day onwards. In US service the 155mm Gun equipped 49 artillery battalions, 40 in Europe and 7 in the Pacific. It made its combat debut in Tunisia in 1943, serving with the 34th Field Artillery Battalion. In service the gun was a great success, and proved to be very accurate even at long range.

The 155mm Gun M1A1 was also give to Britain, who received 184, and France, who received 25, under lend-lease.

155mm Gun M1 being towed, Rendova

After the war the US altered its weapon designations, and the 155mm Gun became the M59.

A total of 1,882 155mm Gun M1A1s were built - 3 in 1940, 62 in 1941, 439 in 1942, 598 in 1943, 526 in 1944 and 254 in 1945.

The 155mm was also produced in a self propelled version. This was the M40 155mm Gun Motor Carriage, which was based on the chassis of the M4A3E8 Sherman. This entered production in 1945, and saw most service during the Korean War. 

155mm Gun M1 ‘Long Tom’ and 8in Howitzer in WWII and Korea, David Doyle. A photographic history of the closely related 155mm Gun and 8in Howitzer, two key pieces of American artillery during the Second World War and in Korea. Includes a brief history of the gun, a section of detailed pictures of parts of the guns, a chapter on the machines used to tow and supply the guns, while the largest chapter, filling half of the book, looks at the two guns combat record in the Second World War and Korea (Read Full Review)

Help - F.A.Q. - Contact Us - Search - Recent - About Us - Privacy