155 mm Long Tom

Not to be confused with the French-built 155 mm Creusot Long Tom, a Boer War artillery piece.

M1 155 mm Long Tom
Long Tom in travelling position, US Army Ordnance Museum.
Type	Towed field artillery
Place of origin	United States
Service history
Used by	United States Italy Australia Austria Japan Jordan South Korea Republic of China Turkey Pakistan Croatia South Africa United Kingdom
Wars	World War II, Korean war, Croatian War of Independence
Production history
Designed	1930s
Specifications
Weight	Travel: 13,880 kg (30,600 lb)
Barrel length	6.97 m (22 ft 10 in) L/45
Crew	14
Caliber	155 mm (6.10 in)
Breech	Asbury breech
Carriage	M1 Carriage
Elevation	−2°/+65°
Traverse	60°
Rate of fire	40 rounds per hour
Muzzle velocity	853 m/s (2,799 ft/s)
Maximum firing range	23.7 km (14.7 mi)

The 155mm Long Tom was a 155 millimeter caliber field gun developed and used by the United States mililtary. It was produced in M1 and M2 variants (later known as the M59). Developed to replace the Canon de 155mm GPF, the gun was deployed as a heavy field weapon during World War II and the Korean War, and also classed as secondary armament for seacoast defense. The gun could fire a 45.36 kg (100 lb) shell to a maximum range of 22 km (13.7 mi), with an estimated accuracy life of 1,500 rounds.

The Long Tom was also adopted by a number of other nations, including the United Kingdom, Austria, Israel, and the Netherlands.

Development

Before entering World War I, the United States was poorly equipped with heavy artillery. To address this problem a number of foreign heavy artillery guns were adopted, including the Canon de 155 mm GPF. The Westervelt Board, established after WW1 to consider the lessons from the recent conflict and to set objectives for future artillery noted that the consensus among artillery experts from a number of countries that heavy field guns should have a range of 25,000yards and an elevation of 65°. It was noted that the French 155mm GPF (adopted by the US Army as the M1918) was outranged by the German 150mm M1916 gun by 5,500yards and was slow to come into action After the end of the war development work began in the United States on a design to improve upon the existing models of heavy gun and carriage. A number of prototypes were produced in the 1920s and 1930s, but the projects were put on hold due to lack of funds. In 1938 the 155 mm Gun T4 on Carriage T2 was finally adopted as 155 mm gun M1 on Carriage M1.

155 mm gun M1

The new gun design used a barrel similar to the earlier 155 mm GPF, but with an Asbury breech that incorporated a vertically-hinged breech plug support. This type of breech used an interrupted-thread breech plug with a lock that opened and closed the breech by moving a single lever. The ammunition for the 155 mm gun was "separate-loading", that is with the shell and the powder charge are packaged, shipped and stored separately. The shell is lifted into position behind the breach and then rammed into the chamber to engage the shell's rotating band into the barrel rifling.

Ramming the shell home is followed by loading a number of powder bags, as required for the desired range. The powder charge could be loaded in up to seven charge settings. Once the powder is loaded, the breech plug is closed and locked, and a primer is placed in the breech plug's firing mechanism. After setting the elevation and azimuth, the gun is ready to fire. The firing mechanism is a device for initiating the ammunition primer. The primer then sets off the igniter which ignites the propelling charge of the ammunition. A continuous-pull lanyard first cocks the firing pin, then fires the primer when pulled.

The gun was developed into M1A1 and M2 variants. After World War II, the United States Army re-organized, and the gun was re-designated as the M59.

Carriage M1

The gun carriage provides a stable, yet mobile, base for the gun. The new split-trail carriage featured an eight-wheel integral two-axle bogie and a two-wheel limber that supported the trails for transport. The carriage was a two-piece design. The upper carriage included the side frames with trunnion bearings that supported the recoil mechanism that carried the gun cradle, slide and gun tube. The upper carriage also incorporated the elevating and azimuth gearing. The upper carriage pivoted in azimuth on the lower carriage. The lower carriage included the transport suspension and the split-trail that stabilized and absorbed recoil when the gun was fired.

The carriage consists of a combination of the following major components:

Bottom carriage	Top carriage
Firing support base	Elevating mechanism
Trails	Traversing mechanism
Retractable suspension system	Gun support components
Axle	Equilibrator
Brakes	Cradle (Connects gun assembly to the top carriage)
Wheels	Recoil mechanism
	Sleigh (Sliding support for the gun tube)
	Gun tube

After the gun was placed in a firing position with the gun pointing in the desired direction, the trails were lowered to the ground and the limber was removed. The carriage wheels would then be raised using built-in ratcheting screw-jacks, lowering the gun carriage to the ground. Once on the ground, the limber-end of the trail legs were separated to form a wide "vee" with its apex at the center of the carriage pivot point. A recoil spade at the limber-end of each trail leg required a correctly positioned hole to be dug for the spade, which was attached to the trail end, to transmit the recoil from gun carriage through the trails and into the earth. This made the gun very stable and assisted its accuracy. The removable spades were transported in brackets on the trail legs.

The carriage M1 and M2 were shared with the 8 inch Howitzer M1, differing only in the gun tube, sleigh, cradle, recoil and equilibrators, weight due to the heavier barrel.

Specifications

Specifications from TM9-350

Weight of gun (complete with breech mechanism)	9,595 lb (4,352 kg)
Weight of tube assembly (barrel)	9,190 lb (4,169 kg)
Length of tube	277.37 in (7.05 m)
Length of bore	cal. 45 (274.6 in / 6.975m)
Length of rifling	230.57 in.
Powder pressure (normal pressure with maximum charge in a new gun)	40,000 psi (275,790 kPa)
Type of breechblock	Interrupted screw
Weight of breech mechanism	405 lb (184 kg)
Type of firing mechanism	continuous pull percussion hammer

Service

Long Tom at crew training in England

The Long Tom saw combat for the first time in North African Campaign on December 24, 1942, with "A" Battery of the 36th Field Artillery Battalion. Eventually it equipped about 49 battalions, including 40 in the European Theater and 7 in the Pacific. The preferable prime mover was initially the Mack NO 6×6 7½ ton truck; from 1943 on it was replaced by the tracked M4 High Speed Tractor.

A small number of Long Tom guns were authorised for supply via lend lease channels, to the United Kingdom (184) and France (25). However, the authorised establishment of British batteries (excluding training units), including four batteries from the Dominion of Newfoundland, totalled 88 guns.

Variants

M2 during the Battle of Okinawa.

Gun variants:

• M1920 – prototype.
• T4 – prototype.
• M1 (1938) – first production variant, 20 built.
• M1A1 (1941) – modified breech ring.
  • M1A1E1 – prototype with chromium plated bore.
  • M1A1E3 – prototype with liquid cooling.
• M2 Standard (1945) – with modified breech ring.

Carriage variants:

• T2 – prototype.
• M1 (1938).
• M1A1 – refurbished T2 carriages.
• M2 Standard

Limber variants:

• M1 Standard (1938)
• M5 Heavy (1945)

M40 in the US Army Ordnance Museum.

The gun was also mounted on a modified M4 medium tank chassis, in mount M13. The resulting vehicle was initially designated 155 mm Gun Motor Carriage T83 and eventually standardized as 155 mm Gun Motor Carriage M40. 155 mm Gun Motor Carriage T79, based on T23 Medium Tank chassis, never advanced past proposal stage. A portable "Panama mount" M1 was also provided.

Ammunition

British gunners cleaning Shells, Italy, February 1945

The gun utilized separate loading, bagged charge ammunition. The propelling charge consisted of base (9.23 kg) and increment (4.69 kg). The data in the table below is for supercharge (base and increment).

Projectiles.
Type	Model	Weight	Filler	Muzzle velocity	Range
APBC/HE	AP M112 Shell	45.36 kg (100.0 lb)	Explosive D	2746 ft/s (837 m/s)	24,075 yds (22,014 m)
HE	HE M101 Shell	42.96 kg (94.7 lb)	TNT	2800 ft/s (853 m/s)	25,714 yds (23,513 m)
Smoke	WP M104 Shell	44.53 kg (98.2 lb)	White phosphorus (WP)	2800 ft/s (853 m/s)	25,940 yds (23,720 m)
Smoke	FS M104 Shell		Sulfur trioxide in chlorosulfonic acid	2800 ft/s (853 m/s)	25,940 yds (23,720 m)
Chemical	H M104 Shell		Mustard gas, 5.3 kg (12 lb)	2800 ft/s (853 m/s)	25,940 yds (23,720 m)
Dummy	Dummy Mk I Projectile		–	–	–
Dummy	Dummy M7 Projectile	43.09 kg (95.0 lb)	–	–	–

Armor penetration, mm
Ammunition / Distance, m	457	914
AP M112 Shell (homogeneous armor, meet angle 30°)	160	152
AP M112 Shell (face hardened armor, meet angle 30°)	135	130
Concrete penetration, mm
Ammunition / Distance, m	914	4572
HE M101 Shell (meet angle 0°)	2,011	1,402
Different methods of measurement were used in different countries / periods. Therefore, direct comparison is often impossible.

Existing examples

Austria

• Bunkermuseum Wurzenpass, Wurzen Pass (near Villach)

Israel

• Batey ha-Osef Museum,Tel Aviv, Israel

Netherlands

• Wings of Liberation Museum Park in Best (near Eindhoven), Netherlands

United Kingdom

• Pendennis Castle, Cornwall, UK

United States

• Battleship Memorial Park, Mobile, Alabama
• Timber Linn Park, Albany, Oregon, see an aerial photo on Google Maps
• US Army Ordnance Museum, Aberdeen, Maryland
• VFW Zachary Taylor Post 3784, Baton Rouge, Louisiana.
• Georgia Veterans Memorial State Park, Cordele, Georgia
• Fort Sill Field Artillery Museum, Fort Sill, Oklahoma
• VFW Post 2330, Searcy, AR
• Museum of American Armor, Old Bethpage, New York

See also

• List of U.S. Army weapons by supply catalog designation SNL D-24
• 15 cm Kanone 18 German equivalent
• 152 mm gun M1935 (Br-2) Soviet equivalent, only built in small numbers
• Cannone da 149/40 modello 35 Italian equivalent, only few built

External links

• 155-mm. Novel Mechanical Features Give Big-Gun Power, Small Gun Speed, November 1942, Popular Science early article with many photos and detailed drawings showing how it is brought into firing position from travel mode.