- QF 13 pounder 9 cwt
Infobox Weapon
name=QF 13 pounder 9 cwt anti-aircraft gun
caption=Australians watching a 13 pdr 9 cwt anti-aircraft gun, Morbecque,Third Battle of Ypres , August 29 1917. The neck in the cartridge is visible.
origin=UK
type=anti-aircraft gun
is_ranged=yes
is_artillery=yes
is_UK=yes
service= 1915 - 1920s [Hogg & Thurston state it was declared obsolete in British service in 1921 but continued in service with the Canadian and Dutch armies for several more years]
used_by=British Empire
wars=World War I
designer=
design_date=
manufacturer=
unit_cost=
production_date=
number=
variants=
weight=7.5 tonsHogg & Thurston 1972, page 65]
length=
part_length=Bore convert|92.62|in|m|sigfig=4; Total convert|96.96|in|m|sigfig=4
width=
height=
crew=
caliber= convert|3|in|mm|sigfig=3|sing=on
cartridge= convert|12.5|lb|kg|sigfig=3Shrapnel ; later HE
action=
rate=8 rds/min
velocity=convert|2150|ft/s|m/s|sigfig=3Routledge 1994, page 9 quotes muzzle velocity convert|1990|ft/s|m/s|sigfig=3. Hogg & Thurston 1972, page 65 quote 2150 ft/second]
range=
max_range=convert|19000|ft|m|sigfig=3 [Farndale 1986, page 132, 364]
feed=
sights=
breech=
recoil=Hydro-spring, constant.
convert|24|in|mm|sigfig=3 (Mk III mount); convert|35|in|mm|sigfig=3 (Mk IV mount)Hogg & Thurston 1972, page 65]
carriage=high-angle mounting on lorry
elevation=0° - 80°
traverse=360°The 13 pounder 9 cwt anti-aircraft gun became the standard mobile British anti-aircraft gun of theWorld War I era, especially in theatres outside Britain. 13 pounder referred to the weight of the shell, 9 cwt referred to the weight of the barrel and breech (9 x 112 lb = 1008 lb), to differentiate it from other varieties of "13 pounder".History
Earlier anti-aircraft guns based on 13 pounder and 18 pounder guns proved unsatisfactory. This weapon combined an 18 pounder breech and barrel with a liner (sleeve) inserted to reduce the bore from convert|3.3|in|mm|sing=on to convert|3|in|mm|sing=on so that it could fire the slightly smaller 13 pounder shell but still use the larger cartridge and propellant charge of the 18 pounder resulting in a much higher velocity. A slight neck was introduced in the 18 pounder cartridge to hold the slightly narrower 13 pounder shell in place.
The initial Mk III mounting was based on the 13 pounder Mk II anti-aircraft mounting, but proved to be not strong enough for the extra power of the 18 pounder cartridge.
The Mk IV mounting which followed raised the height by convert|9|in|mm and increased recoil from 24 to convert|35|in|mm and hence relieved the strain on the mounting.Hogg & Thurston 1972, page 64]
Several guns are known to have been mounted on 2-wheeled high-angle field carriages and deployed on the Italian front. Hogg & Thurston state that they could theoretically be used as anti-aircraft guns, field guns or howitzers, but they were not officially introduced and may have been of an experimental nature. [Hogg & Thurston 1972, page 66-67] Routledge states that the carriage was improvised because some of 4th AA Group's guns had arrived in Italy without mountings.Routledge 1994, page 33]
Combat use
As World War I progressed, it was replaced in the home air defence of England (against German heavy bombers) by the more powerful
QF 3 inch 20 cwt gun, but continued in all other theatres. It was usually deployed mounted on medium lorries such as the Thornycroft Type J with a speed of 18 miles per hour, in sections of 2 guns.On the Western Front they were typically used to protect troop columns, airfields, bases, supply dumps and observation balloons. [Routledge 1994, page 32]
As important as the raw performance of the gun itself was the new technology being developed to allow fast calculation of aircraft height and predict where it would be when the shell arrived near it. Modern aircraft could fly at over 100 miles per hour and to 20,000 ft (much lower over the battlefield) by 1918, which made the old reliable artillery shooting techniques obsolete. The shell took 10.1 seconds to reach convert|5000|ft|m|abbr=on fired at 25° above horizontal, 15.5 seconds to reach convert|10000|ft|m|abbr=on at 40°, 22.1 seconds to reach convert|15000|ft|m|abbr=on at 55°.Routledge 1994, page 9] Hence the aircraft position had be calculated 10 - 22 seconds in advance and fuzes needed to be set to explode at the correct height.
By the end of World War I a 13 pounder AA Section was accompanied by 2 Wilson-Dalby Trackers with a rudimentary electronic computer to provide tachymetric prediction, a UB2 rangefinder, a Height/Fuze Indicator (HFI) and an Identification telescope. German fighters countered by attacking at low level - a few hundred feet. AA guns would continue to fire but the shells would then explode over the heads of those they were defending. But it brought attacking aircraft within range of defensive machine guns. Few aircraft were actually directly shot down, each requiring an average 4,000 - 4,500 shells, [Routledge 1994, page 20, 24, 23] but guns were often employed in aerial barrages to deny an airspace to aircraft rather than to simply shoot down individually targeted aircraft. Brigadier Routledge notes than "in the BEF [i.e. on the Western Front] stress was laid on long-range deterrent fire; indeed in Fourth Army this was the BRA's stated policy. 'Kills' were therefore less common. Moreover, gun and fighter zones were not separated, as in Britain, and this made set plans for action less workable". [Routledge 1994, page 21]
Routledge further comments that in World War I British cooperation between infantry and anti-aircraft sections was generally rudimentary. However, he points out a successful integration in the Allied advance on the Piave in Italy in late 1918, where S and V Batteries of 4th AA group used their 13 pdr 9 cwt guns to provide mobile air and ground fire in close support of infantry. This tactic later became common in World War II.Routledge 1994, page 33]
At the end of World War I, a total of 306 were in service worldwide, 232 of these on the Western Front (out of a total 348 AA guns there). [Routledge 1994, page 27]
Performance
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