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Newton 6-inch mortar

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

Newton 6-inch mortar
Canadian troops firing the 6-inch (152.4 mm) mortar in the open at Valenciennes in 1918
TypeMedium mortar
Place of originUnited Kingdom
Service history
In service1917–1918
Used byBritish Empire
United States
WarsWorld War I
Production history
DesignerCaptain H Newton, 5th Btn Sherwood Foresters
Designed1916
No. builtUK : 2,538[1]
Specifications
Barrel lengthBore: 4 ft 6 in (1.37 m)
Total: 4 ft 9 in (1.45 m)[2]
ShellHE 52 lb (24 kg)[3]
Calibre6 inches (152.4 mm)
Elevation77°–45°
Rate of fire8 rounds/min[4]
Effective firing range100 - 1,420 yds
(91 - 1,298 m)
Maximum firing range1,950 yd (1,780 m)[5]
FillingAmatol, Ammonal or Sabulite
Filling weight22 pounds (9.98 kg)

Description

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The Newton 6-inch replaced the 2-inch medium mortar beginning in February 1917.

It was a simple smooth bore muzzle-loading 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

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Loading bomb in a typical trench emplacement, Mesopotamia 1918

British Empire divisions were initially equipped with three batteries of four mortars designated X, Y and Z. From February 1918 onwards, these were consolidated into two batteries, X and Y, of six 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 one 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, 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 four vanes (fins), consisting of a specially loaded blank .303 rifle cartridge. The basic propellant charges were contained in four small white cambric bags each containing 1 oz of guncotton yarn. These were held in place in the four angles between the bomb's fins. For ranges less than 1000 yards, one 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 two white cambric bags each containing 1 oz 4 drm of 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

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52 lb bomb, ML 6-inch trench mortar
Propellant : 1-4 one ounce guncotton charges in the base of the bomb, plus an 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
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See also

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Weapons of comparable role, performance and era

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Surviving examples

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Notes and references

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  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

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  • 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
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