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Written by David Boyd   
Thursday, 01 January 2009 14:47

The Bofors 40mm Anti-Aircraft Gun

                Bofors Anti-Aircraft Gun   Bofors Anti-Aircraft Gun

The Bofors anti-aircraft gun was developed by a Swedish company in the late twenties and in 1937 the War Office decided to buy 100 guns and 500,000 rounds of ammunition. This initial order was later followed by a license to build them in Britain. Production began before the outbreak of war but only 233 had been produced by September 1939, production was slow but rapidly increased to fill the increasing anti-aircraft requirements. The practical rate of fire is generally listed as 120 round per minute.

Unlike other nations such as Germany, the British never held smaller calibre anti-aircraft weapons such as the 20mm in much regard as while generally having a higher rate of fire which meant a greater change of achieving a hit they lacked sufficient power to guarantee severe damage to the aircraft. In 1938 the Royal Aircraft establishment calculated that it would require 4 ounces of cyclonite to destroy a modern aircraft wing. A 20mm calibre weapon carries around 0.425 ounces while a Bofors 40mm round about 2 ounces. As you can see the 20mm was quite underpowered, trails against a Blenheim Bomber showed that 20mm ammunition generally only caused severe damage if it hit a vital area such as the controls or fuel tanks. Hits from a Bofors gun were generally much more severe.

A semi armour piercing round was produced for the Bofors in 1941 followed by a full armour piercing round at the beginning of the next year. These rounds were to provide protection against enemy armoured vehicles such as tanks. Around a million of these rounds were produced by the United Kingdom during the war, I have not yet come across decent penetration figures yet, a May 1941 document gives around 25mm, 30 degrees, 1300 yards for what is probably the SAP round, the full AP round probably had performance similar to that of the 2 Pounder anti-tank gun.

Bofors Carriage Data

  Mk I mounting, Mk I platform Mk III mounting, Mk I platform Mk III mounting, Mk II platform Mk II mounting static
Total weight with gun 4,368lb 5,110lb 5,418 2,632
Overall Length (Travelling) 20'-6" 20'-6" 21'-4" -
Overall Length (Firing) 17' 17' 16' 12'-9"
Overall Width (Travelling) 6'-4" 6'-4" 6'-1.25" -
Overall Width (Firing) 13'-3" 13'-3" 13'-2" 6'-1.25"
Overall Height (Travelling) 6'-1" 6'-1" 6'-5.625" -
Overall Height (Firing) 13'-3" 13'-3" 5'-5.5" 4'-4"
Max Elevation 90 90 90 90
Max Depression 5 5 5 5
Calibre 56.25 56.25 56.25 56.25

Cartridge Data

Mark Charge Projectile Length Weight
HE Mk IT 320 grams cordite IT 17.59" 4.8lb
HE Mk IIT 320 grams cordite IT 17.59"  
HE Mk IIIT 0.613lb W.T. IT 17.59"  
HE Mk IVT 0.563lb W.T. IIT 17.59"  
HE Mk VT 0.68 W.T. IIT 17.59"  

Projectile Data

Mark Length Width Width (band) Shell Weight Bursting Charge Total Weight
HE Mk IT 6.8" 1.56" 1.63" 1.85lb 0.125lb TNT 2.2lb
HE Mk IIT 5.13" 1.56" 1.63" 1.37lb TNT or 0.148lb RDX/BW 2lb
SAP Mk I 6.17" 1.56" 1.63" 2.37lb - -

Ballistic data

   HE Mk IT HE Mk IIT
Muzzle velocity 2789fps 2850fps
Max horizontal range 12,500 yards 10,750 yards
Max height 26,000 feet 22,900 feet

Production of Bofors Guns by year *Commonwealth data is from May 1942 onwards.

  Pre-War Sep-Oct 1939 1940 1941 1942 1943 1944 1945 (May)
Bofors Equipments 233 49 1,062 2,678 5,025 3,661 556 -
Bofors SP - - - - 10 1,458 210 -
 Airborne version - - - - 16 238 9 -
 Bofors for Crusaders - - - - 1 225 - -
Bofors Equipments (Canada) - - - - 1,311 1,427 501 -
Bofors Equipments (Other) - - - - 8 155 58 -

Sources - British & American Artillery of WWII, AVIA 22 456 - 514, Bofors Handbook

Last Updated on Thursday, 01 January 2009 14:48
 

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