155 mm gun M1

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 Austria Japan Jordan South Korea Republic of China Turkey Pakistan Croatia South Africa United Kingdom
Wars	World War II, Korean war
Production history
Designed	1930s
Specifications
Mass	Travel: 13,880 kg (30,600 lbs)
Barrel length	6.97 m (22 ft 10 in) L/45
Crew	14
Caliber	155 mm (6.1 inch)
Breech	Asbury breech
Carriage	M1 Carriage
Elevation	−2°/+65°
Traverse	60°
Rate of fire	40 rounds per hour
Muzzle velocity	853 m/s (2,800 ft/s)
Maximum firing range	23.2 km (14.4 mi)

The 155 mm Gun M1 and M2 (later M59), widely known as Long Tom, were 155 millimeter calibre field guns used by the United States armed forces during World War II and Korean War. The Long Tom replaced the Canon de 155 mm GPF in United States service.

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. 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.

The 155 mm gun M1

The new design used a barrel broadly similar to the earlier 155 mm GPF, but used an Asbury breech mechanism that incorporated a vertically-hinged breech plug support. This type of breech used a breach plug with an interrupted thread lock that opened the breech with a single lever.

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

The Carriage M1

The new split-trail carriage featured an eight-wheel integral two-axle boogie 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.

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 tha 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 was shared with the 8 inch Howitzer M1, differing only in the gun tube, sleigh, cradle, recoil and weight due to the heavier barrel.

Service

Long Tom at crew training in England.

M2 during the Battle of Okinawa.

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 6x6 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

M40 in the US Army Ordnance Museum.

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 (1945) – modified breech ring.

Carriage variants:

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

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.

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, kg	Filler	Muzzle velocity, m/s	Range, m
APBC/HE	AP M112 Shell	45.36	Explosive D	837	22,014
HE	HE M101 Shell	42.96	TNT	853	23,513
Smoke	WP M104 Shell	44.53	White phosphorus (WP)	853	23,720
Smoke	FS M104 Shell		Sulfur trioxide in Chlorosulfonic acid	853	23,720
Chemical	H M104 Shell		Mustard gas, 5.3 kg	853	23,720
Dummy	Dummy Mk I Projectile		–	–	–
Dummy	Dummy M7 Projectile	43.09	–	–	–

 

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

• US Army Ordnance Museum
• Timber Linn Park, Albany, Oregon

Aerial Photo on Google Maps

• VFW Zachary Taylor Post 3784, Baton Rouge, Louisiana.

Pendennis Castle, Cornwall, UK

See also

• List of U.S. Army weapons by supply catalog designation SNL D-24

References

• Bishop, Chris. Encyclopedia of Weapons of World War II. ISBN 0-7607-1022-8.
• Hunnicutt, R. P. (1994). Sherman: A History of the American Medium Tank. Presidio Press. ISBN 0-89141-080-5. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Hunnicutt, R. P. (1996). Pershing, A History of the Medium Tank T20 Series. Feist Publications. ISBN 1-112-95450-3. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Zaloga, Steven J. (2007). US Field Artillery of World War II. New Vanguard 131. illustrated by Brian Delf. Osprey Publishing. ISBN 978-1-84603-061-1. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Hunnicutt, R. P. (1996). Pershing, A History of the Medium Tank T20 Series. Feist Publications. ISBN 1-112-95450-3. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Technical Manual TM 9-3305, Principles of Artillery Weapons. Department of the Army, May 1981. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Technical Manual TM 9-1901, Artillery Ammunition. War Department, 1944. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
• Technical Manual TM 9-1904, Ammunition Inspection Guide. War Department, 1944. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)

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.