QF 13-pounder 6 cwt AA gun
|QF 13 pounder 6 cwt anti-aircraft gun|
On Mk II mounting on Thornycroft Type J lorry, Armentières March 1916
|Place of origin||United Kingdom|
|Used by||British Empire|
|Wars||World War I|
|Barrel length||Bore: 5 feet 9 inches (1.753 m);
Total: 6 feet 1 inch (1.854 m)
|Shell||12.5 pounds (5.67 kg) Shrapnel; later HE|
|Calibre||3-inch (76.2 mm)|
|Recoil||hydro-spring, constant, 25 inches (635 mm)|
|Carriage||high-angle mounting on lorry|
|Maximum firing range||17,000 ft (5,200 m)|
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.[i]
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. 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. On the Mk II mount the gun has the appearance of a standard 13 pounder.
Following World War I, the guns were returned to service as standard 13 pounder field guns.
The gun's performance was "ballistically poor" 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.
The following table 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)|
|QF 13 pounder Mk III||1600||12.5||?||?||?||17,000|
|QF 13 pounder 9 cwt||1990[ii]||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|
|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||2350||31 (4.38/6 c.r.h.)||?||?||?||31,000|
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