Squid (weapon)

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Squid anti-submarine mortar on display at the Devonport Naval Base

Squid was a World War II ship-mounted anti-submarine weapon. It consisted of a three-barrelled mortar which launched depth charges. It replaced the Hedgehog system, and was in turn replaced by the Limbo system.

Literally ordered directly from the drawing board in 1942, this weapon was rushed into service in May 1943 onboard HMS Ambuscade. The first production unit was installed on HMS Hadleigh Castle, it went on to be installed on 70 frigates and corvettes during the second world war. The first successful use was by HMS Loch Killin on 31 July 1944, when she sank U333. The system was credited with 17 submarines in 50 attacks. 195 squid installations had been produced by 1959.

This weapon was a three-barrel 12 inch (305 mm) mortar with the mortars mounted in series but off-bore from each other in order to scatter the projectiles. The barrels were mounted in a frame that could be rotated through 90 degrees for loading. The projectiles weighed 390 lb (177 kg) with a 207 lb (94 kg) minol ¹ charge. Sinking speed was 43.5 ft/s (13.3 m/s) and a clockwork time fuse was used to set the depth. Maximum depth was 900 feet (274 m) and all three projectiles had to be set the same.

The weapons were automatically fired from the sonar range recorder at the proper moment. The pattern formed a triangle about 40 yards (37 m) on a side at a distance of 275 yards (250 m) ahead of the ship. Most squid installations utilised two sets of mortars. All six bombs were fired in salvo so that they formed opposing triangular spreads. The salvos were set to explode 25 feet (7.6 m) above and below the target, the resulting pressure wave crushing the hull of the submarine.

In April 1977, the Type 61 frigate Salisbury became the last ship to fire the Squid in Royal Navy service.

[edit] General characteristics

Calibre: 12 in (305 mm)
Projectile weight: 440 lb (200 kg)
Explosive charge: 207 lb (94 kg)
Range: 275 yards (250 m)
Sinking speed: 43.5 ft s^-1 (13.3 m s^-1)
Installation weight: 10 tons

[edit] Notes

Note 1: Due to shortages of TNT and RDX (cyclonite) in World War II, the British used a 50/50 mixture of ammonium nitrate and TNT (amatol) in naval mines and depth charges. This low grade explosive was later improved by the addition of about 20% aluminium powder, producing minol.