Newton 6 inch Mortar

Newton 6 inch Mortar
Canadian troops firing the 6-inch (152.4 mm) Mortar in the open at Valenciennes in 1918
Type	Medium mortar
Place of origin	United Kingdom
Service history
In service	1917 - 1918
Used by	British Empire  United States
Wars	World War I
Production history
Designer	Captain H Newton, 5th Btn Sherwood Foresters
Designed	1916
Number built	UK : 2,538[1]
Specifications
Barrel length	Bore: 4 ft 6 in (1.37 m) Total: 4 ft 9 in (1.45 m)[2]
Shell	HE 52 lb (24 kg)[3]
Calibre	6 inches (152.4 mm)
Elevation	77°–45°
Rate of fire	8 rounds/min[4]
Effective range	100 - 1,420 yds (91 - 1,298 m)
Maximum range	1,950 yd (1,780 m)[5]
Filling	Amatol, Ammonal or Sabulite
Filling weight	22 pounds (9.98 kg)

The Newton 6 inch Mortar was the standard British medium mortar in World War I from early 1917 onwards.

Description

The Newton 6 inch replaced the 2 inch Medium Mortar beginning in February 1917.

It was a simple smooth bore muzzle-loading (SBML) mortar consisting of a 57-inch (1,448 mm) one-piece steel tube barrel, with a "striker stud" inside the centre of the closed base of the tube. The rounded external base of the tube sat in a socket in the flat cast steel base, which in turn sat on a wooden platform. An "elevating guy" (cable) connected to a loop in the upper side of the barrel and the rear end of the bed. "Traversing guys" (cables) connected to loops on each side of the barrel and eyebolts on the upper sides of the bed. Hence aiming of the barrel was done by adjusting the length of the guys via adjusting screws. A socket in the barrel base allowed for emergency firing via a "misfire plug" in the case of misfires (i.e. if the bomb remained in the barrel due to failure of the propellant to ignite).^[6]

Combat service

Loading bomb in typical trench emplacement, Mesopotamia 1918

British Empire Divisions were initially equipped with 3 batteries of 4 mortars designated X, Y, Z. From February 1918 onwards these were consolidated into 2 batteries, X and Y, of 6 mortars each, and Z was dissolved. In British use they were operated by the Royal Field Artillery and formed part of the Divisional Artillery with 1 battery attached to each of the Divisional artillery brigades.

The United States Army began production and equipping with this mortar late in the war but it is doubtful whether any were used in combat.

3rd Australian Medium Trench Mortar Battery in action, Ville-sur-Ancre, Somme, 29 May 1918

The mortar was operated from concealed pits close to the front line during trench warfare, and was used in the open during the final "mobile warfare" phase of the First World War, as demonstrated in the photograph, depending on available transport. The disassembled weapon was usually transported on horsedrawn carts but the Canadian Automobile Machine Gun Brigade (the Canadian Independent Force or "Brutinel's Brigade") is known to have successfully used the mortar both mounted on motor trucks and dismounted in the closing months of the war.^[7][8]

The 52-pound cast-iron fin-stabilised high explosive bomb carried the percussion primer at the base in the intersection of the 4 vanes (fins), consisting of a specially loaded blank .303 rifle cartridge. The basic propellant charges were contained in 4 small white cambric bags each containing 1 oz of guncotton yarn. These were held in place in the 4 angles between the bomb's fins. For ranges less than 1000 yards 1 or more bags could be removed, as per range tables.

For ranges above 1,000 yards (910 m), additional charges were loaded before the bomb, held in 2 white cambric bags each containing 1 oz 4 drm cordite.^[9]

In action the gunners would adjust the angle of the barrel via the elevating guy (for distance) and traversing guys (for direction). The manual warns: "See that the elevating and traversing screws of the guys are always tight. A slack guy leads to inaccurate shooting, and the stresses on firing are not equally distributed; this is usually the cause of the guys breaking".^[10]

The range tables specified the barrel angle and propellant charges required. The additional cordite propelling charge bags were dropped down the barrel if necessary, or necessary number of propellant charges removed from the bomb, and the bomb's fuze was set. The gunners stood back, the bomb was dropped down the barrel, the detonator in the base of the .303 cartridge in the base of the bomb struck a pin in the bottom of the barrel and fired, igniting the guncotton charges in the base of the bomb, which in turn ignited the cordite charges if present. The resulting rapid gas expansion propelled the bomb up the barrel and to its target.

1917 Range tables

52 lb Bomb, ML 6 inch Trench Mortar.
Propellant : 1-4 one ounce guncotton charges in the base of the bomb, plus optional 2.5 oz cordite charge.^[11]

Range (yards)	1 oz charge degrees	2 oz charge degrees	3 oz charge degrees	4 oz charge degrees	4 oz + 2.5 oz cordite
					degrees	seconds
100	77
120	74
140	71
160	67.5
180	63.5
200	59
220	47.5	77.25
226	45
240		76
260		74.75
280		73.25
300		72
320		70.5	77.5
340		69	76.75
360		67.5	76
380		66	75
400		64.25	74.25
420		62.25	73.25
440		60.25	72.25	77.25
460		57.75	71.5	76.5
480		55	70.5	76
500		50.5	69.5	75.25
510		45
520			68.5	74.5
540			67.5	74
560			66.25	73.25
580			65.25	72.5
600			64	72
620			62.75	71.25
640			61.25	70.5
660			59.75	69.75
680			58.25	69
700			56.5	68.25	75.25	23.9
720			54.5	67.5	74.75	23.9
740			51.75	66.75	74.25	23.8
760			45.5	65.75	73.75	23.8
761			45
780				65	73.25	23.7
800				64	72.75	23.6
820				63.25	72.25	23.6
840				62.25	71.75	23.5
860				61	71.25	23.4
880				60	70.75	23.4
900				58.75	70.25	23.3
920				57.5	69.75	23.2
940				56	69.25	23.1
960				54.5	68.75	23.1
980				52.5	68.25	23.0
1000				50	67.5	22.9
1016				45
1020					67	22.8
1040					66.5	22.7
1060					66	22.6
1080					65.25	22.5
1100					64.5	22.8
1120					64	22.2
1140					63.25	22.1
1160					62.75	22.0
1180					62	21.8
1200					61.25	21.7
1220					60.5	21.5
1240					59.5	21.3
1260					58.75	21.1
1280					57.75	20.9
1300					56.75	20.7
1320					55.75	20.4
1340					54.75	20.2
1360					53.5	19.9
1380					52	19.5
1400					50	19.0
1420					45	17.5

Image gallery

• 

  Men of the 9th Btn Royal Sussex Regt and mortar bomb dump near Lens, September 3 1918
• 

  Mk III bomb diagram
• 

  Bomb at Hawthorn Crater, Somme 1998. Photograph by Marco Hoveling http://www.unfortunate-region.org

See also

• List of heavy mortars

Surviving examples

• Army Memorial Museum, Waiouru, New Zealand
• Royal Australian Artillery Museum, North Head, Sydney, Australia
• Australian Army Infantry Museum, Singleton NSW Australia

Notes and references

1. ^ Ministry of Munitions 1922, pages 130-131
2. ^ Preliminary Notes on the M.L. 6-Inch Trench Mortar Mark I. 1917
3. ^ 52 lb total weight for bomb is quoted in Range Tables. Preliminary Notes on the M L 6-inch Trench Mortar, Mark I. Handbook of the M L 6-inch Trench Mortar Mark I.
4. ^ Ministry of Munitions 1922, page 66
5. ^ A maximum range of 1,950 yards was eventually achieved after improvements. Ministry of Munitions 1922, page 66
6. ^ Preliminary Notes on the M.L. 6-Inch Trench Mortar, Mark I, 1917, page 1
7. ^ Michael Holden, University of New Brunswick, "Training, Multi-National Formations, and Tactical Efficiency: The Canadian Motor Machine Gun Brigades in 1918"
8. ^ Danish Military History Society, "The Canadian Motor Machine Gun Brigade, Part 1"
9. ^ Handbook of the M.L. 6-Inch Trench Mortar Mark I. 1918
10. ^ Handbook of the M.L. 6-Inch Trench Mortar Mark I. 1918, page 10
11. ^ Preliminary Notes, 1917

Bibliography

• Preliminary Notes on the M.L. 6-Inch Trench Mortar Mark I. 1917. War Office, UK.
• Handbook of the M.L. 6-Inch Trench Mortar Mark I. 1918. War Office, UK.
• W L Ruffell, "An example of Kiwi ingenuity. A carriage designed by the Divisional Trench Mortars to meet the changed conditions of fighting in the last advances of 1918"
• Handbook of artillery : including mobile, anti-aircraft and trench matériel (1920). United States. Army. Ordnance Dept, May 1920
• "History of the Ministry of Munitions", 1922. Volume XI, Part I Trench Warfare Supplies. Facsimile reprint by Imperial War Museum and Naval & Military Press, 2008 ISBN 1-84734-885-8

External links

• The Imperial War Museum holds a manuscript detailing Captain Newton's work on this and other weapons
• "Provisional drill regulations for trench mortar batteries; 6" Newton and the 240 mm. : chapters II, VI, and VIII". United States. War Dept, 1918. Made available online by Combined Arms Research Library
• "Handbook on trench mortar fuzes, Mark VII and Mark VII-E.". United States. War Dept, 1918. Made available online by Combined Arms Research Library
• "Manual for trench artillery, United States Army (provisional). Part I, trench artillery.". United States. War Dept, July 1918. Made available online by Combined Arms Research Library
• "Manual for trench artillery, United States Army (provisional). Part II, formations and maneuvers". United States. War Dept, 1918. Made available online by Combined Arms Research Library
• WL Ruffell, The 6-inch Mortar from "The Mortar"
• An Unfortunate Region