155-mm Gun M1
When the United States entered World War I in 1917 it was ill-equipped with heavy artillery, and consequently was issued with various Allied artillery models, including the French 155-mm (6.1-in) GPF (Grand Puissance Filloux). This gun was one of the best of its type at that time, but in the years after 1918 the American design teams sought to improve the overall efficiency of the gun and carriage by introducing a series of prototypes throughout the 1920s. Sometimes this programme stood in abeyance for years, but by the late 1930s the new design (very basically the original GPF barrel equipped to accommodate an Asbury breech mechanism) was standardized as the 155-mm Gun M1 on Carriage M1, and production started at a steady pace at various American arsenals.
The M1 gun and carriage combination was very much an overall improvement on the old French GPF design, but introduced some new features. The barrel was 45 calibres long, and the carriage was of a heavy splittrail type carried on four double-tyred road wheels forward. This carriage arrangement was such that in action the wheels were lifted to allow the carriage to rest on a forward firing platform that in use proved to be an excellent arrangement and very stable. This stability made the gun very accurate, and eventually the carriage was adopted by the British for use with their 7.2-in (183-mm) howitzer. For towing the trail legs were hitched up on to a limber device. There were two of these, the M2 and the M5, the latter having a rapid up-and-over lift arrangement that permitted quick use in action but which could also be dangerous to an untrained crew. For this reason the M2 limber was often preferred.
The M1 was gradually developed into an M1A1 form and then into the M2 in late 1944. These changes were mainly limited to production expedients and did not affect the gun's performance, which proved to be excellent: a 43,1-kg (95-lb) shell could be fired to a range of 23221 m (25,395 yards). The M1 soon became one of the standard heavy guns of the US Army and was often used for counter battery work. Numbers were issued to various allied nations, and the M1 was soon part of the British army gun park, which used the type in action in Europe from the Normandy landings onwards. The M1 also went selfpropelled. This was carried out using a much-modified M4A3E8 Sherman tank chassis with the gun mounted in an open superstructure, and in this form the vehicle/gun combination was known as the M40. It was 1945 before the M40 actually got into production so its main career was post-war but it was widely used by many nations, again including the UK.
After 1945 the US Army underwent a period of internal reorganization and in the process the M1 and M2 guns became the M59. The post-war period also saw the end of the limber devices for it was discovered that with most of the heavy tractors used to pull the guns all that was needed was to join the trails and connect them direct to the tractor towing eye, usually with chains. In this form the 155-mm (6.1-in) M59 serves on to this day with many armies around the world. It is still a good gun, although now considered to be rather lacking in range and range flexibility as a result of the fixed charges used, and it is gradually being replaced by more modern designs. But it will still be some years before it is replaced in the armies of nations such as Austria, South Korea, Taiwan and Turkey.
Specification 155-mm Gun M1A1
Calibre: 155 mm (6.1 in)
Length of piece: 7.366 m (24 ft 2 in)
Weight: travelling 13880 kg (30,600 lb) and in action 12600 kg (27,778 lb)
Elevation: -2∞ to +65∞
Muzzle velocity: 853 m (2,800 ft) per second
Maximum range: 23221 m (25,395 yards)
Shell weight: 42 kg (92,6 lb)