| 240 mm trench mortar | |
| Origin: | France |
| Type: | Heavy trench mortar |
| Is Ranged: | yes |
| Is Explosive: | yes |
| Is Artillery: | yes |
| Is Uk: | yes |
| Service: | 1915–1918 |
| Used By: | France United States Italy Austria-Hungary |
| Wars: | World War I |
| Designer: | Dumezil-Batignolles |
| Design Date: | 1915 |
| Weight: |
|
| Part Length: | 2m (07feet) (including breech) |
| Crew: | 7 |
| Cartridge: | HE 81.6kg (179.9lb) (US & France) |
| Caliber: | 240mm |
| Rate: | 1 per 6 min |
| Velocity: | 145 m/s (475 ft/s) (max charge) |
| Range: | 603 - 2,071 m (660 – 2,265 yd) |
| Breech: | Vertical sliding block |
| Elevation: | 75° to 45° |
| Traverse: | 18° left & right |
| Filling: | Amatol or ammonal |
| Filling Weight: | 40kg (90lb) |
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 weapon was dismantled for transport, requiring four 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.".[1] Its 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 in mid-1918.
The mortar was first introduced in 1915 as the Mortier de 240 mm CT (court de tranchee). It was a short barreled version which fired a 192lb bomb for 1125yd, using a propellant charge of 1lb.[2]
Its first major use was in the Champagne offensive of September 25, 1915.
This was followed later by the Mortier de 240 mm LT (long de tranchée) which was a long barreled version with improved firing arrangement and breech-loaded charge which fired a 179lb bomb, using a propellant charge of 2lb.[2] This appears to be the bomb configuration adopted by US.
French estimates were 80 bombs needed to destroy a strong shelter with a roof of concrete or rails and concrete.[3]
David Lupton's Sons Co manufactured the weapon in the United States during World War I. They were used by nine trench mortar battalions of the Coast Artillery Corps.[4]
The US version appears to have been a direct copy of the Mortier de 240 mm LT, i.e. with longer barrel and propellant charge loaded into the breech via a brass cartridge case, was also produced late in the war but it is doubtful whether any were actually used in combat. The December 1917 manual describes the weapon as "9.45 inch" but makes clear it is the French 240 mm they are describing that the US has adopted. The bomb is described as weighing 180lb, with an explosive charge of 90lb and range from 660 to .[1]
The March 1918 manual describes the Bomb, Model 1916, Type T, weight 183lb, explosive 93lb, length 1.02m (03.35feet). Barrel and breech weighing 690lb, carriage 448lb, base 764lb, timber platform 5720lb. Propellant charges of 800 grams Ballistite + 15 grams F-3 black powder for 750–1,400 meters, and 1250 grams Ballistite + 15 grams F-3 for 1,100–2,200 meters.[5] This figure agrees with the charge quoted for the mortar in French use for maximum range.
"Separate loading ammunition" was used i.e. the mortar bomb was a separate unit from the propellant cartridge case, which was flanged, brass, 9.776 inches long x 6.67inches diameter (248.3 by 169.4 mm).[6] The bomb was loaded into the barrel muzzle. The cartridge containing propellant charge appropriate for the required range was loaded into the breech, similar to a howitzer.
The mortar was fired by pulling a lanyard, which activated a primer located in the base of the cartridge case, igniting the propellant charge inside. After firing, the cartridge cases could be reused following cleaning and replacement of the primer.
Italy adopted and manufactured both the French CT (Bombarda da 240 C) and LT (Bombarda da 240 L) mortars.[7] [8] Mortar groups were established with 240 C, 240 L, and 58A (Mortier de 58 mm type 2) batteries, which were split in December 1916 into batteries of 58A and 240mm mortars. The 240mm battery consisted of 4 sections with 2 mortars each, and a combined staff of 7 officers, 215 men, 62 horses, a baggage wagon, and 4 bicycles. By the end of 1916 510 240mm mortars were still in service.[9] After World War I ended some of the 240mm mortars were exported to Montenegro.[10]
Some 400 were copied and manufactured by Böhler during World War I based on examples captured from Italy,[11] although the Austrians had problems recreating the original powder mixture and their shells suffered from large dispersions.[12]
See main article: 24 cm schwere Flügelminenwerfer IKO. The US A.E.F. in France reported in March 1918 : "... a new pattern minenwerfer which was brought out in 1916 and looks very much like the French 240... uses a heavy bomb fitted with four vanes like the French 240 mm bombs. This bomb weighs 100kg (200lb) and contains 42kg (93lb) of explosive... ranges obtained vary from 490yd1310yd".[13] The specifications appear similar to the early French 240 mm CT quoted above. It is unknown whether this was related to the French or Austrian Böhler versions.
