QF 13-pounder 6 cwt AA gun

The Ordnance QF 13 pounder Mk III anti-aircraft gun, also known as 13 pounder 6 cwt, was an early British improvisation in World War I to adapt the 13 pounder field gun to anti-aircraft use. 6 cwt referred to the weight of barrel and breech (6 × 112 lb = 672 lb) to differentiate it from other "13 pounder" guns.[lower-roman 1]

QF 13 pounder 6 cwt anti-aircraft gun
On Mk II mounting on Thornycroft J Type lorry, Armentières March 1916
Type	Anti-aircraft gun
Place of origin	United Kingdom
Service history
In service	1915–1918[1]
Used by	British Empire
Wars	World War I
Production history
No. built	20
Specifications
Barrel length	Bore: 5 feet 9 inches (1.753 m); Total: 6 feet 1 inch (1.854 m)[2]
Shell	12.5 pounds (5.67 kg) Shrapnel; later HE
Calibre	3-inch (76.2 mm)
Recoil	hydro-spring, constant, 25 inches (635 mm)[2]
Carriage	high-angle mounting on lorry
Elevation	0°–70°[2]
Traverse	360°
Maximum firing range	17,000 ft (5,200 m)[2]

History

On Mk I mount, on a Daimler Mk 3 lorry

This was a standard QF 13 pounder field gun barrel and breech with the addition of a retaining catch to the breech to retain the round when loading at high angles.[3]

It was first approved in October 1914 and was issued on Mk I high angle mounting, usually mounted on a motor lorry. The Mk I mounting had an additional recuperator housing mounted directly above the normal recuperator to facilitate gun runout at high angles.[3] Hence the appearance was of a gun barrel with 2 slightly shorter tubes of similar diameter above it.

Mk II mount improved the usability, added deflection gear and the recoil system was improved so that the additional recuperator became unnecessary and was removed.[3] On the Mk II mount the gun has the appearance of a standard 13 pounder.

The mount design was unusual in having both gunlayers on the left side.[1]

Following World War I, the guns were returned to service as standard 13 pounder field guns.

Combat use

The gun's performance was "ballistically poor"[1] and it was only marginally effective against aircraft. It was relegated to minor war theatres and the 13 pounder 9 cwt and 3 inch 20 cwt guns took over the major anti-aircraft role.

At the end of World War I there were only 20 of the guns in service worldwide, with 12 in Egypt and Palestine, 4 in Mesopotamia, 2 in Greece (Salonika front) and 2 on the Western Front.[4]

Performance

The following table[5] compares the gun's performance with the other British World War I anti-aircraft guns:-

Gun	m/v ft/s	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 (ft)[6]
QF 13 pounder Mk III	1600	12.5	?	?	?	17,000
QF 13 pounder 9 cwt	1990[lower-roman 2]	12.5	10.1	15.5	22.1	19,000
QF 12 pdr 12 cwt	2200	12.5	9.1	14.1	19.1	20,000
QF 3 inch 20 cwt 1914	2500	12.5	8.3	12.6	16.3	23,500
QF 3 inch 20 cwt 1916	2000	16	9.2	13.7	18.8	22,000[8]
QF 4 inch Mk V World War I	2350	31 (3 c.r.h.)	4.4 [sic]	9.6	12.3	28,750
QF 4 inch Mk V World War II[9]	2350	31 (4.38/6 c.r.h.)	?	?	?	31,000

See also

• List of anti-aircraft guns

References

1. In common terminology, they were classified by shell weight
2. Routledge[5] quotes muzzle velocity 1,990 feet per second (607 m/s). Hogg & Thurston[7] quote 2,150 feet per second (655 m/s)

1. Routledge (1994), p. 6.
2. Hogg & Thurston (1972), p. 61.
3. Hogg & Thurston (1972), p. 60.
4. Routledge (1994), p. 27.
5. Routledge (1994), p. 9.
6. Hogg & Thurston (1972), pp. 234–235.
7. Hogg & Thurston (1972), p. 65.
8. Routledge (1994), p. 13.
9. World War II details from Tony DiGiulian's website

Bibliography

• Hogg, I.V.; Thurston, L.F. (1972). British Artillery Weapons & Ammunition 1914-1918. London: Ian Allan. ISBN 978-0-7110-0381-1.CS1 maint: ref=harv (link)
• Routledge, Brigadier NW (1994). History of the Royal Regiment of Artillery. Anti-Aircraft Artillery, 1914-55. London: Brassey's. ISBN 978-1-85753-099-5.CS1 maint: ref=harv (link)