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BL 7.5-inch naval howitzer

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The BL 7.5-inch howitzer (naval) was a British anti-submarine mortar developed during World War I.

BL 7.5-inch naval howitzer
On SS Boonah
TypeAnti-submarine mortar
Place of originUnited Kingdom
Service history
In service1917 - 192?
Used byBritish Empire
WarsWorld War I
Specifications
MassGun & breech 812 pounds (368 kg)[1]
Barrel lengthBore 63.75 inches (1.619 m)[1]
ShellHE 100 pounds (45.4 kg)
Calibre7.5-inch (191 mm)
Breechsingle-motion interrupted screw
Muzzle velocity480 feet per second (146 m/s)
Maximum firing range2,100 yards (1,920 m)
FillingTNT
Filling weight43 pounds (19.5 kg)[2]

History

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7.5-inch howitzer HMS Vindictive IWM Q 20555

The weapon was developed together with other similar devices early in 1917 and went into service in June 1917 in response to German unrestricted submarine warfare. It was mounted on merchant ships and patrol vessels. By 10 December that year, 377 were in service.[3]

The shell was fired at the submarine either on the surface or submerged - hence it had attributes of both armour-piercing shell and depth charge. It was designed to first penetrate the submarine's outer hull without breaking up, and then detonate against the inner hull after a 2-second delay,[1] destroying the submarine. However the small weight of the shell limited its effectiveness,[3] and the anti-submarine mortar did not become a truly successful weapon until the advent of the multiple-projectile Hedgehog during World War II.

Nonetheless Admiral John Jellicoe, writing a few years after the gun had gone into service, commented: "This weapon, although not very popular at first, soon, however, proved its value, when employed both from patrol craft and from merchant ships."[3]

Two were mounted on HMS Vindictive and used to bombard German defences during her participation in the Zeebrugge raid of 23 April 1918.

Similar weapons

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  • 12 cm/12 short naval gun - A Japanese anti-submarine gun used during World War II.
  • 20 cm/12 short naval gun - A Japanese anti-submarine gun used during the latter half of World War II.
  • 8-inch Mark 7 & Mark 8 - Two American anti-submarine guns designed late in World War I that never entered service.

Notes and references

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  1. ^ a b c Hogg and Thurston 1972, Pages 148-149
  2. ^ Standard shell was 100 lb, containing 43 lb TNT. In early 1918 a 500 lb stick bomb containing 250 lb TNT was developed, with a range of 300 yards. Hogg & Thurston 1972, page 148
  3. ^ a b c Jellicoe, 1920. Chapter III

Bibliography

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