‍ ‍Ammunition.

(i) Explosive Ordnance.

When considering the employment of catapults in trench warfare, we should view them as grenade launchers, since most of the available ammunition was modified hand grenades, such as making them slightly larger and heavier to carry a larger payload of explosives or chemicals. In the absence of an adequate supply of special bombs, crews for both the Leach catapult and West Spring Gun were quite promiscuous in their choice of explosive ordnance, using the double-cylinder grenades or the notoriously unsafe No 14 (heavy) pitcher grenades and, from the beginning of 1916, the Mills bomb.

The details of how these bombs were fired have not survived, but given what we know about the importance of fitting a properly designed throwing pouch to the Leach catapult, it is probable that the use of unsuitable ammunition contributed to the view that bomb throwers were unsafe and unreliable. Several high explosive fills, gun cotton, TNT or ammonal, were used, although their relatively small payload limited their utility to cause damage, and for the earliest bombs, the Fuze was a simple match-head composition lit with a naked flame or burning cigarette.

Later, Brock or Nobel igniters were introduced, providing some protection against damp conditions, and the burn time increased to 7 or 9 seconds to accommodate the longer flight time of the bomb before it exploded. It was widely recognised that percussion fuses would be more reliable, but there were inherent difficulties in developing such a complex fuse for a small bomb, and it was almost impossible to ensure that a round bomb would always land on the detonator, so, irrespective of type, all catapult bombs were fitted with a simple time fuse and detonator.[1]‍ ‍

Until the introduction of the Mills bomb, the similarities between the ammunition for trench catapults and hand grenades often led to competition for manufacturing resources, with priority given to grenades. In preparing for the Battle of Loos, the First Army planners envisaged a role for the Leach Catapult as a close-support weapon carried forward with the attacking infantry. Its ammunition was a slightly enlarged No 15 Ball grenade, 3 inches in diameter, containing a useful charge of 6 oz. amatol, which, when fitted with fuse and detonator, weighed just over 2 lbs. Their manufacture employed the same facilities as those required for the No 15 Ball grenade, but, as this was about to be declared obsolete, the Trench Warfare Department promised as many catapult bombs as desired, but issues with the new Mills bomb meant it would not be available to equip the First Army, and the manufacture of the Ball grenade was reinstated. Without ammunition, the usefulness of the catapults in the battle was severely limited.[2]‍ ‍

Once the manufacturing problems with the Mills had been resolved, the Trench Warfare Department switched back to the catapult pattern, producing 100,000 a week, with a quarter going to the Dardanelles. They also promised a weekly output of 40,000 of the new D grenades, the heavier version of the No 15, four inches in diameter and containing twice as much high explosive, and a small supply of the experimental E bombs, a three-inch diameter version of the D grenade containing 8 ounces of amatol, but few of these were produced before the catapult was declared obsolete.

(ii) Smoke Bombs.

Smoke, and to a lesser extent, chemical bombs, were commonly used with catapults. Smoke bombs for the Leach catapults were tin cylinders, 5 inches by 3 inches, containing 1 lb of red phosphorus, generating smoke for 10 minutes. A typical formula for maintaining an adequate smoke screen was one bomb every 10 minutes for every 10 ft of frontage covered by the catapult. A much more destructive bomb, filled with Threlfallite, a mixture of white phosphorus and petrol, was also available, and although occasionally used as a smoke generator, it was predominantly an incendiary device to clear trenches, dugouts, or set fire to enemy localities and strong points. The West Spring gun could fire these bombs.

(iii) Chemical Bombs.

The original chemical bombs for the Leach Catapult were metal cylinders 5 inches long by 5 inches in diameter, but were a bad fit and often fell out of the throwing pouch when the catapult was fired, and it took several weeks of experimentation to determine that a slightly smaller cylinder fitting a specially designed pouch could be fired safely.[3]

These cylinder bombs were superseded in the late summer of 1915 when Colonel Jackson developed the Type Q chemical bomb. The first chemical bombs issued to the BEF for catapults were filled with a variety of non-lethal chemicals, including sulphur dioxide, a respiratory irritant; carbon disulphide, a chemical widely used in pest control that produces intense sneezing, difficulty in breathing and is fatal in high concentrations or after prolonged exposure. In an attempt to increase the effectiveness of these chemicals, a pinch of capsicin, a powerful sternutator extracted from chilli peppers, was added.[4]

Others were filled with ‘Hillite’, a mixture of capsicin and magnesium carbonate or ‘Westonite’, a mixture of sulphur chloride and bromine, of which a total of 18,220 were issued to the BEF. All these grenades were developed in the belief that they might be useful for clearing enemy trenches and dugouts, but given their small size, it is unlikely that an effective concentration of any of the chemicals was achieved unless several bombs could be lobbed into an enclosed dugout at the same time.

In January 1916, GHQ ruled that bombs and grenades filled with these non-lethal chemicals had no military value and should be discontinued. The exceptions were grenades containing SK or phosphorus. Ethyl iodoacetate (codename SK), a powerful tear gas, was the non-lethal chemical of choice for the BEF throughout the war. It was sufficiently reactive to attack the solder that held the components of the tin bomb together, which were contained in special glass flasks that fitted inside the bomb casing, held in place by felt pads to prevent accidental breakage.

This is one of the earliest chemical grenades and consisted of a tin-plate cylindrical shell 5.3 inches long and 3 inches in diameter, with two end caps: the bottom one fixed and the top one removable. Chemical fill is contained in a glass container fitted internally and held in place on felt-lined tin cylinders soldered to the end caps. A copper sleeve to receive the No. 8 Detonator was formed in the base of the container, and two copper binding wires were soldered into the bottom cover to retain the Brock Lighter. The grenade was projected from a catapult or spring gun, and the chemical was released when the tin was broken open by detonation of the No 8 Detonator.

With no SK available, this grenade was filled with either sulphur chloride and bromine (Westonite Grenade) or sulphur dichloride (Eastonite Grenade). This was a variation on the No 15 Ball grenade, consisting of a spherical cast-iron body 3.9 inches high and 3.3 inches in diameter, with an internally threaded neck to take a cast-iron closing cap and burster tube. A copper binding wire is attached to the lug on the closing cap to retain the Brock Ignighter, comprising the Fuze, Safety fuse, and the Detonator, a No 8 Mk VII. Filled and fitted with the Igniter, it weighed 2.26 lbs., and without, 1.5 lbs. It held 220 cc of the lachrymator S.K. The grenade was produced under War Office directives in 1915 for use with SK and was designed to be projected from a catapult or spring gun but could also be thrown by hand. The grenade was reintroduced in 1916 as Grenade No 28 Mark I. The purpose of this grenade was for clearing dugouts, and for identification, it was marked with a white band.  

In 1916, this grenade was used to trial White Star, a lethal chemical combination of chlorine and phosgene, but such grenades do not appear to have been adopted for service, perhaps because of the inherent danger to the thrower or friendly troops in the vicinity.

‍ [1] It was not until 1917 that the problem of a percussion fuse for mortar bombs was resolved with the introduction of the ‘All-Ways’ percussion fuse. [2] History of Ministry of Munitions XI Part I, p. 89. The munitions audit of 11 November 1915 reported that the BEF was equipped with 364,005 grenades, of which 2/3 (288,092) were Ball grenades

[3] Addison c76. Folio 97-98: 1st report of the chemical sub-committee. 18/8/15

[4] Sternutator is an agent that causes powerful sneezing, coughing, and sometimes vomiting.