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M1 / M2 155mm "Long Tom" Towed Gun

The M2 "Long Tom" was the mainstay of Army corps level artillery in the latter stages of WWII and the Korean War. This gun could also be mounted on a M40 or M43 self propelled gun carriage. The "Long Tom" was known for accuracy at long Range.

The 155-mm guns M1, M1A1, and M2 can be mounted on either the M1 or M1A1 gun carriages. The 155-mm guns M1 and M1A1 are identical with one exception. The 155-mm gun M1 has a breech ring bushing inserted in the breech ring. The breech mechanism female threads are cut in the breech bushing. The 155-mm gun M1A1 does not have a breech ring bushing; the breech mechanism female threads being cut directly in the breech ring. The 155-mm gun M2 is similar in construction to the 155-mm gun M1, i.e., the breech ring is fitted with a breech ring bushing and the breech mechanism female threads are cut in the breech ring bushing. In addition the 155-mm gun M2 has a slightly larger powder chamber than the guns M1 or M1A1.

The 155-mm gun M2 is used as a heavy field weapon and is also classed as secondary armament for seacoast defense. The 155-mm gun M2 is mounted on three types of mounts, namely; the heavy field carriage M1 or M1A1, gun motor carriage T83 and the firing platform M1. The 155-mm gun carriages M1 and M1A1 are heavy field carriages and are equipped with a bogie assembly at the front of the carriage, which is used to lower the carriage to the firing position and also to raise the carriage to the traveling position. The carriage is limbered by either the heavy limbers M2 or MS, or it can be towed without the use of the limber by being semi-trailed. When emplaced, removable spades are installed on the carriage and on the rear ends of the trails. Air brakes are provided for use during transit, and hand brakes are applied on the front bogie wheels when the weapon is parked.

The firing platform M1 is a circular platform designed to enable all-around fire. When mounted on the firing platform M1, the same materiel is used that is used with the heavy gun carriage M1 and M1A1. The weapon is rolled up into place and anchored on the bolster in the center of the platform. The gun motor carriage M40 provides a highly mobile heavy artillery unit. When mounted on the 155-mm gun mount M13 for mounting on the gun motor carriage, only the gun, recoiling parts and top carriage of heavy field materiel are used.

The recoil mechanism is a hydro-pneumatic type with a variable recoil feature to offset differences of recoil at various degrees of elevation. The 155-mm gun M2 may be equipped with either the firing mechanism M1 or the firing lock M17. Separate loading ammunition is used, which is loaded and rammed into the gun by hand.

The 155-mm gun carriage M1 was the standard carriage for these guns. The M1A1 carriages were the original test models re worked to be practically identical with the M1 carriage. Differences that remain between these two models are manufacturing details. The heavy carriage limbers M2 and MS are entirely different in design and operation.

The French, who had lost 377,000 at Verdun alone, were more than willing to share their artillery with the exuberant doughboys whose eyes were still unscarred by the wanton slaughter of modern warfare and whose biggest field piece was the 3-inch howitzer. One of the ordnance pieces lent by the French was the 155-mm gun, called the Grande Puissance Filloux (GPF)—literally "Filloux's gun of great power." Weighing 25,500 pounds underway and 20,100 pounds in firing position, it could hurl a 95-pound explosive shell over 17,000 yards.

Its official adoption by the American Expeditionary Force (AEF) came, when the US Army labelled it the M1917 155-mm gun. The subsequent M1918 was merely an American-manufactured version of the French gun. All one had to do to transform a GPF into the M1917A1 was to fit an American breechblock to the French gun. Expertly handled by doughboy crews, this gun—sometimes referred to as the 155-mm rifle—pounded the German lines.

The memory of the French 155-mm gun's uncanny accuracy, long range, and destructive prowess was still fresh in the minds of cannoneers when they were queried by the Westervelt Board just months after the Armistice. This group of ordnance and artillery officers had been convened to canvas its own and foreign artillerymen as to the relative merits of different cannon, as well as what they envisioned would be most desirable on any future battlefield. One of the Board's recommendations, submitted on 23 May 1919, called for a new improved 155-mm gun, with the extra proviso that a self-propelled version also be developed.

Since the Board's specifications for both the 155-mm gun and the 8-inch howitzer were nearly identical, the ordnance planners — faced by the inevitable shortage of research and development funds once the fighting stopped — decided to design a single carriage capable of mounting either of the two new weapons.

The newly designed 155-mm gun measured 22 feet, 10.7 inches long (not including the breech), weighed 9,200 pounds, and could fire a 95-pound projectile over 26,000 yards. The resultant dual-purpose carriage, along with the new 155-mm gun and 8-inch howitzer, was designed as the M1920E. Spring suspended, the carriage alone weighed 18,800 pounds. The maximum elevation was 65 degrees and total traverse was 60 degrees for the 155-mm gun, while the Filloux type variable recoil mechanism permitted a maximum recoil of 60 inches and a minimum recoil of 24 inches.

The carriage's hard rubber tired wheels, while adequate for the slow moving tractors then used to move field artillery, made it obsolete for any fast-moving mechanized army. The carriage proved unstable when the gun was fired at maximum power, and, as an additional handicap, the M1920E model had been specifically designed to be divided into two separate loads for transportation, particularly when crossing bridges.

The Ordnance Department tinkered with several other experimental carriages during the 1920s, but without success. Then, in the summer of 1930, Rock Island Arsenal developed the radical split-trail T2 carriage which contained at least two "firsts" for heavy field artillery carriages: an all-welded construction and a unique 8-wheel (four dual tires) roll-bearing bogie that permitted the gun to be carried on truck wheels cross-country at high speeds. For stability in the firing position, special built-in jacks (which eliminated the need for a crane) dropped the bottom carriage to the ground. This T2 carriage survived for over 30 years without any major modification.

Meanwhile, both a new 155-mm gun and 8-inch howitzer had been designed to share this radical T2 carriage, being type-classified standard as the M1 in July 1940. The M1 155-mm gun soon gave way to the improved M1A1 in June 1941 which, in turn, was superseded in March 1945 by the M2 (model designation changes reflected the different type construction of the tube and breech ring). On 9 August 1945, the unconverted M1 and M1A1 were declared obsolete.

The United States, still reeling from the catastrophic effects of the Great Depression, however, did not feel it could afford the luxury of big expensive guns; therefore, only 65 Long Toms were built before 1941. Left over from th Great War, however, and still carried on the army inventory were 908 French GPFs, some of which had been modified for high speed towing.

The Long Toms quickly earned the respect and admiration of all that came without sound or striking range of its mighty blast. In the war years to come, both the European and Pacific theaters were to witness its accuracy and deathly punch.

Armament: 155mm gun

Crew: 8-10

Weight: 5,765 lbs

Rate of Fire: 40 rds/h

Range: 23,500 yds

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Page last modified: 29-05-2019 19:05:28 ZULU