9.45 inch Heavy Mortar

9.45 inch Heavy Trench Mortar
Australians loading a 9.45-inch (240 mm) trench mortar, Battle of Pozières, France, August 2 1916.
Type	Heavy siege mortar
Place of origin	France
Service history
In service	1915 - 1918
Used by	United Kingdom Australia
Wars	World War I
Production history
Designer	Dumezil-Batignolles
Designed	1915
Number built	712^[1] (UK)
Specifications
Weight	Mortar & elevating gear 499 lb, + body & bed 987 lb (Mk I) 644 lb, + 1169lb (Mk II - IV)^[2]
Barrel length	51 inch (Mk I) 69 inch (Mk II - IV)^[2]
Crew	7

Shell	HE 152 lb (UK)^[2]
Calibre	240 mm (9.45 inch)
Elevation	75° - 45°
Traverse	18° L & R
Rate of fire	1 per 6 min
Muzzle velocity	475 ft/s (max charge)
Effective range	660 - 2,400 yd (2,200 m)
Filling	amatol or ammonal

This large calibre mortar of World War I originated as a French design, the Mortier de 240 mm developed by Batignolles Company of Paris and introduced in 1915. Britain manufactured a modified version under license as the 9.45 inch Heavy Trench Mortar, nicknamed the "Flying Pig"^[3] and it was the standard British heavy mortar from Autumn 1916 onwards.

1 History
2 Combat use
3 Notes
4 References
5 See also
6 Surviving Examples
7 External links

History

The British ML 9.45-inch (240 mm) mortar was a design based on the French 240 mm mortar in 1915 and introduced in 1916. The British version differed from the French LT weapon in that the propellant charge was loaded through the muzzle^[4] whereas the French 240 mm had the charge loaded through the breech in a brass cartridge case.

General Farndale states that in June 1916 following unsatisfactory trials with the French model Britain replaced them with 30 of its own model, firing a 150 pound bomb, followed by 200 more in December 1916.^[5]

The Mark 1 with 51-inch (1,300 mm) barrel was introduced from June 1916. In 1917, the Mark 2 and Mark 3 followed with 69-inch (1,800 mm) barrel, and small numbers of Mark 4^[1].

Combat use

It was operated by crews of the Royal Garrison Artillery which was the British Army service branch that operated the heaviest artillery, formed into batteries of 4 mortars attached to each division, designated "V/nn" where nn = division number. From February 1918 they were reorganised and moved from divisional to corps control.

The weapon was dismantled for transport, requiring 4 carts for the barrel, base, carriage and ammunition.

In action, a heavy timber platform was constructed embedded in the ground, on which the mortar base was immovably secured. The mortar carriage sat on the base and could traverse. The mortar barrel and breech were mounted on the carriage which provided elevation.

They were used in the "siege warfare" on the Western Front to destroy enemy strongpoints, bunkers and similar "hard" targets which were invulnerable to lighter mortars and field guns. The US Army handbook described it : "... the use for which it is primarily adapted is in the bombardment of strongly protected targets - dwellings, covered shelters, command posts, entrances to galleries, etc - or in the destruction of sectors of trenches, salients and the like."^[6]. Their effectiveness decreased late in the war as German policy changed to a lightly held frontline, hence decreasing available targets, and they became redundant when the war of movement resumed late in 1918.

Both the propellant charge appropriate for the required range and the bomb were loaded via the muzzle. Usually a Lee-Enfield rifle's bolt action mechanism was screwed into the breech. A special blank rifle cartridge was loaded and was triggered by pulling a lanyard, and fired into an igniter at the base of the mortar chamber, igniting the propellant charge and launching the bomb^[1].

Notes

^ ^a ^b ^c Kevin Robert Keefe, British 9.45-inch (240 mm) Heavy Trench Mortar, Mark III
^ ^a ^b ^c Handbook of the M.L. 9.45 inch Trench Mortars. February 1918. War Office, UK.
^ The precise origin of the nickname "flying pig" is unclear. Some sources describe the bomb as looking like a small pig in flight; it may also refer to the English language term meaning an unlikely event (as in "pigs might fly"), deriving from the clumsy bulky appearance; it may be a mixture of both.
^ "Manual for trench artillery, United States Army (provisional). Part I, Trench Artillery.". Prepared at Headquarters AEF, France, March 1918. page 8
^ General Sir Martin Farndale, History of the Royal Regiment of Artillery. Western Front 1914-18. London: Royal Artillery Institution, 1986. Annex G, Trench Mortar Organization in France, page 367.
^ "Handbook of the 9.45-inch trench mortar matériel" United States Ordnance Department. December 1917. page 9