QF 4-inch naval gun Mk V

The QF 4 inch Mk V gun^{[note 1]} was a Royal Navy gun of World War I which was adapted on HA (i.e. high-angle) mountings to the heavy anti-aircraft role both at sea and on land, and was also used as a coast defence gun.

Ordnance QF 4 inch gun Mk V
QF 4 inch HA guns aboard the cruiser HMAS Sydney, 1939–1940
Type	Naval gun Anti-aircraft gun Coastal defence gun
Place of origin	United Kingdom
Service history
In service	1914–1945
Used by	British Empire
Wars	World War I World War II
Production history
No. built	944[1]
Specifications
Mass	Barrel & breech: 4,890 lb (2,220 kg)[2]
Barrel length	Bore: 15 ft (4.6 m) (45 cal) Total: 15 ft 8 in (4.8 m)[2]
Shell	31 lb (14.1 kg) fixed QF or Separate-loading QF
Calibre	4-inch (101.6 mm)
Breech	horizontal sliding-block
Recoil	hydro-pneumatic or hydro-spring 15 inches (380 mm)
Elevation	mounting dependent
Traverse	mounting dependent
Muzzle velocity	2,350 ft/s (716 m/s)[2]
Maximum firing range	Surface: 16,300 yd (15,000 m)[3] AA: 28,750 ft (8,800 m)[2]
Filling	Lyddite, Amatol
Filling weight	5 pounds (2.27 kg)

Service

Naval service

LA (Low Angle) gun and crew on HMS Galatea, February 1917

LA (Low Angle) gun on HMAS Vampire firing circa 1938

This QF gun was introduced to provide a higher rate of fire than the BL 4 inch Mk VII. It first appeared in 1914 as secondary armament on Arethusa-class cruisers, was soon adapted to a high-angle anti-aircraft role. It was typically used on cruisers and heavier ships, although V and W-class destroyers of 1917 also mounted the gun.

Mk V was superseded by the QF 4 inch Mk XVI as the HA (i.e. anti-aircraft) gun on new warships in the 1930s, but it continued to serve on many ships such as destroyers, light and heavy cruisers in World War II.^[4]

Army anti-aircraft gun

Early in World War I several guns were supplied by the Navy for evaluation as anti-aircraft guns for the home defence of key installations in Britain. They were mounted on static platforms and proved fairly successful after a fixed round was developed to replace the original separate round, and more followed. The AA mounting allowed elevation to 80° but loading was not possible above 62°, which slowed the maximum rate of fire.^[5] At the Armistice, a total of 24 guns were employed in AA defences in Britain and 2 in France.^[6] After World War I, the guns were returned to the Navy.

Coast Defence gun

From 1915 to 1928, several guns were mounted in forts to guard the estuary of the River Humber.^[7]

Anti-aircraft performance

Comparison with the other British World War I anti-aircraft guns^[8]

Gun	muzzle velocity	Shell (lb)	Time to 5,000 ft (1,500 m) at 25° (seconds)	Time to 10,000 ft (3,000 m) at 40° (seconds)	Time to 15,000 ft (4,600 m) at 55° (seconds)	Max. height[9]
QF 13 pdr 9 cwt	1,990 ft/s (610 m/s)	12.5	10.1	15.5	22.1	19,000 ft (5,800 m)
QF 12 pdr 12 cwt	2,200 ft/s (670 m/s)	12.5	9.1	14.1	19.1	20,000 ft (6,100 m)
QF 3 inch 20 cwt 1914	2,500 ft/s (760 m/s)	12.5	8.3	12.6	16.3	23,500 ft (7,200 m)
QF 3 inch 20 cwt 1916	2,000 ft/s (610 m/s)	16	9.2	13.7	18.8	22,000 ft (6,700 m)[10]
QF 4 inch Mk V World War I	2,350 ft/s (720 m/s)	31 (3 c.r.h.)		9.6	12.3	28,750 ft (8,760 m)
QF 4 inch Mk V World War II [11]	2,350 ft/s (720 m/s)	31 (4.38/6 c.r.h.)				31,000 ft (9,400 m)

Ammunition

Ammunition for the original low-angle guns introduced in World War I was Separate QF i.e. the shell and cartridge were separate items, but in World War II most guns used Fixed QF ammunition i.e. a single unit. The fixed Mk V ammunition was 44.3 inches (1.13 m) long and weighed 56 pounds (25 kg), while the projectile was 31 pounds (14 kg).^[12]

• 
  Fixed QF cartridge for LA (low-angle) gun, 1930s
• 
  Crew storing fixed rounds on the Kingfisher class sloop HMS Widgeon, August 1943

See also

• List of anti-aircraft guns
• List of naval guns
• List of naval anti-aircraft guns

Weapons of comparable role, performance and era

• Cannon 102/45 Italian copy of the QF Mk V made under license
• 10.5 cm SK L/45 naval gun Approximate German equivalent firing slightly heavier shell

Surviving examples

• A gun from HMNZS Tutira in front of the Devonport Naval Base, Auckland, New Zealand

Notes

1. Mk V = Mark 5. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Mark V indicates this was the fifth model of QF 4-inch gun.