It was a simple smooth bore muzzle-loading mortar consisting of a 57-inch (1,448mm) 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 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 (910m), 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
52lb 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]
Jonesborough-Washington County History Museum, Jonesborough, Tennessee - Displayed previously in the town square, now part of the Historical Society collection. Produced by Hadfields of Sheffield, England. Unknown how it came to reside in Tennessee.
↑ Preliminary Notes on the M.L. 6-Inch Trench Mortar Mark I. 1917
↑ 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.
"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 ISBN1-84734-885-8
Cordite is a family of smokeless propellants developed and produced in Britain since 1889 to replace black powder as a military firearm propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance. These produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The hot gases produced by burning gunpowder or cordite generate sufficient pressure to propel a bullet or shell to its target, but not so quickly as to routinely destroy the barrel of the gun.
A mortar is today usually a simple, lightweight, man-portable, muzzle-loaded cannon, consisting of a smooth-bore metal tube fixed to a base plate with a lightweight bipod mount and a sight. Mortars are typically used as indirect fire weapons for close fire support with a variety of ammunition. Historically mortars were heavy siege artillery. Mortars launch explosive shells in high-arching ballistic trajectories.
A shell, in a military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. A shell can hold a tracer.
The Ordnance QF 18-pounder, or simply 18-pounder gun, was the standard British Empire field gun of the First World War-era. It formed the backbone of the Royal Field Artillery during the war, and was produced in large numbers. It was used by British Forces in all the main theatres, and by British troops in Russia in 1919. Its calibre (84 mm) and shell weight were greater than those of the equivalent field guns in French (75 mm) and German (77 mm) service. It was generally horse drawn until mechanisation in the 1930s.
The Ordnance BL 60-pounder was a British 5 inch (127 mm) heavy field gun designed in 1903–05 to provide a new capability that had been partially met by the interim QF 4.7 inch Gun. It was designed for both horse draft and mechanical traction and served throughout the First World War in the main theatres. It remained in service with British and Commonwealth forces in the inter-war period and in frontline service with British and South African batteries until 1942 being superseded by the BL 4.5 inch Medium Gun.
This article explains terms used for the British Armed Forces' ordnance (weapons) and ammunition. The terms may have different meanings depending on its usage in another country's military.
The BL 8-inch howitzer Marks VI, VII and VIII were a series of British artillery siege howitzers on mobile carriages of a new design introduced in World War I. They were designed by Vickers in Britain and produced by all four British artillery manufacturers but mainly by Armstrong and one American company. They were the equivalents of the German 21 cm Morser 16 and in British service were used similarly to the BL 9.2-inch howitzer but were quicker to manufacture and more mobile. They delivered a 200 lb (91 kg) shell to 12,300 yd. They had limited service in the British Army in World War II before being converted to the new 7.2 in (180 mm) calibre. They also equipped a small number of Australian and Canadian batteries in World War I and by the US Army in that war. They were used in small numbers by other European armies.
The Livens Projector was a simple mortar-like weapon that could throw large drums filled with flammable or toxic chemicals.
The Stokes mortar was a British trench mortar designed by Sir Wilfred Stokes KBE that was issued to the British and U.S. armies, as well as the Portuguese Expeditionary Corps, during the latter half of the First World War. The 3-inch trench mortar is a smooth-bore, muzzle-loading weapon for high angles of fire. Although it is called a 3-inch mortar, its bore is actually 3.2 inches or 81 mm.
The Ordnance QF 4.5-inch howitzer was the standard British Empire field howitzer of the First World War era. It replaced the BL 5-inch howitzer and equipped some 25% of the field artillery. It entered service in 1910 and remained in service through the interwar period and was last used in the field by British forces in early 1942. It was generally horse drawn until mechanisation in the 1930s.
The 2 inch medium trench mortar, also known as the 2-inch howitzer, and nicknamed the "toffee apple" or "plum pudding" mortar, was a British smooth bore muzzle loading (SBML) medium trench mortar in use in World War I from mid-1915 to mid-1917. The designation "2-inch" refers to the mortar barrel, into which only the 22 in (560 mm) bomb shaft but not the bomb itself was inserted; the spherical bomb itself was actually 9 in (230 mm) in diameter and weighed 42 lb (19 kg), hence this weapon is more comparable to a standard mortar of approximately 5–6 in (130–150 mm) bore.
The ML 9.45 inch heavy trench mortar, nicknamed the "Flying Pig", was a large calibre mortar of World War I and the standard British heavy mortar from the autumn of 1916. It was a modification of an original French design, the Mortier de 240 mm developed by Batignolles Company of Paris and introduced in 1915. Britain manufactured the modified version under licence.
The BL 6-inch gun Mark VII was a British naval gun dating from 1899, which was mounted on a heavy travelling carriage in 1915 for British Army service to become one of the main heavy field guns in the First World War, and also served as one of the main coast defence guns throughout the British Empire until the 1950s.
The 240 mm trench mortar, or Mortier de 240 mm, was a large calibre mortar of World War I. An original French design, it was developed by Batignolles Company of Paris and introduced in 1915.
The Ordnance BL 5-inch howitzer was initially introduced to provide the Royal Field Artillery with continuing explosive shell capability following the decision to concentrate on shrapnel for field guns in the 1890s.
The Ordnance BL 9.2-inch howitzer was a heavy siege howitzer that formed the principal counter-battery equipment of British forces in France in World War I. It equipped a substantial number of siege batteries of the Royal Garrison Artillery. During World War II a limited number were used in the Battle of France, with the remainder being kept in the United Kingdom.
The British BL 6-inch gun Mk XIX was introduced in 1916 as a lighter and longer-range field gun replacement for the obsolescent BL 6-inch gun Mk VII.
The Mortier de 58 mm type 2 or Mortier de 58 mm T N°2, also known as the Crapouillot or "little toad" from its appearance, was the standard French medium trench mortar of World War I.
The Ordnance ML 4.2-inch mortar was a heavy mortar used by the British Army during and after World War II.
A range table was a list of angles of elevation a particular artillery gun barrel needed to be set to, to strike a target at a particular distance with a projectile of a particular weight using a propellant cartridge of a particular weight. They were used for several centuries by field and naval gunners of all countries until gradually replaced by computerised fire-control systems beginning in World War II (1939–1945).
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