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Guns Index

40 mm Bofors

Gun

Mk 1 - Original Swedish manufacture. Type "A" auto-loader
Mk 1* - As Mk 1 but any auto-loader
C Mk 1 - As Mk 1 but Canadian built
C Mk 1* - As Mk 1* but Canadian built
Mk 1/2 - Conversion of Mk 1*. Double baffle muzzle brake. For airborne mountings Mks 7 to 10
Mk 2 - Alloted to Naval design but then withdrawn to avoid confusion with American M2 model
Mk 3 - Wartime production model. Accepted simplified designs of auto-loader
Mk 4 - Naval, water cooled, for twin mounting
Mk 5 - Naval, water cooled, for single mounting
Mk 6 - As Mk 1 but changes to suit mounting in tanks. Used with mounting Mk 6 in Crusader AA tank. Cartridge deflector ejected upwards

Auto-loaders

Type A - Swedish pattern. Took two 4 round chargers, ejected to left
Type A* - Type A with peep sight in rear guide. Only used with Mk 6 gun on tanks
Type B - Simplified design. Took three 4 round chargers, ejected to right
Type C - Non standard Type B made by Chambon Company
Type M - Type B made more reliable
Type M* - Type C made more reliable

Data - Mk 1 on Mounting Mk 1

Wt gun & breech mech - 966 lb
Wt in action - 4,368 lb
Total length - 117.7 inches
Length of bore - 88.58 inches
Rifling - 16 grooves increasing RH 1/54 to 1/30
Breech mech - Vertical sliding block, auto, percussion fired
Elevation - minus 5º to plus 90º
Traverse - 360º
Recoil system - Hydrospring
Recoil length - constant 7.87 inches
Rate of Fire - 120 rpm

Introduced in April 1937, they were later built under licence. British variations included a simplified auto-loader and various types of sight. Towards the end of the war, remote power control was perfected.

Performance

With 2 lb HE shell:
Muzzle velocity - 2,700 ft/sec
Max horizontal range - 10,800 yds
Maximum ceiling - 23,600 feet
Effective ceiling - 5,000 feet

Mountings

Mk 1 - Original Bofors design. Direct laying, prepared for data receiving dials but not fitted
Mk 1A - Polish design. As Mk 1 but not prepared for dials
Mk 1B - British design. As Mk 1 but with laying gears designed for hand or remote power operation. Only 2 made
Mk 2 - Mk 1 modified for remote power control. Non made
Mk 3 - British design. For remote power control
C Mk 3 - Canadian made Mk 3
Mk 3A - As Mk 3 but small changes in hand controls
Mk 3B - As Mk 3A but with modified platform
Mk 4 - As Mk 3B but with "cease firing" switches to prevent firing at dangerous elevations
Mk 4A - As Mk 4 but with laying gear by Linotype Company
Mk 5 - As Mk 4 but modified for mounting on Morris SP carrier
C Mk 5 - Canadian made Mk 5
Mk 5/1 - As Mk 5 but with remote power control removed
Mk 6 - As Mk 4 but modified for use in Crusader AA tanks
Mk 7 - Mk 3 converted to fit airborne 2 wheeled carriage
Mk 8 - Mk 4 converted to fit airborne 2 wheeled carriage
Mk 9 - C Mk 3 converted to fit airborne 2 wheeled carriage
Mk 10 - Canadian made Mk 4 modified to fit 2 wheeled airborne carriage

Platforms (carriages)

Mk 1 - Original Bofors design. Riveted girder, Ackermann steering, independent suspension. Tyres 6 x 20 inch. Hydraulic brakes on rear wheels
Mk 1A - Polish design. Similar to Mk 1
Mk 2 - British design. Fabricated construction, tubular side girders. Trolley steering, no springing. Tyres 9 x 13 inch
C Mk 2 - Canadian built Mk 2
Mk 3 - As Mk 2 but with mechanical over-run brakes on front wheels
Mk 4 - Mk 2 converted for use in aircraft or gliders. Could be broken down into 10 major units
2 wheeled C Mk 1 - Canadian design. For air transportation or jeep towing. 2 girders hinged to form tow bar, third girder telescoped into central section.
Carriage Transporting Mk 1/India - 2 wheeled carriage for air or jeep use. For use in Far East by Indian Army
Carriage Transporting Mk 2/India - As Mk 1 but lighter, without brakes & axle 6 inches shorter
Carriage transporting Mk 2/1 - As Mk 2 but with brakes. For British Army use in Far East
Holdfast Mk 1 - For concrete emplacement. 4 steel beams with 8 holding down bolts
Platform Firing Mk 1 - Temporary wooden structure for emergency use
Platform Firing No. 16 - Steel platform for use with Mk 3 mounting in Maunsell Forts

Self Propelled Mounts
Carrier Morris 40mm AA Mk 1 - 3 ton Morris-Commercial truck with Mk 5 mounting secured to cargo bed
Crusader III AA Tank Mk 1 - Turret removed and replaced by armoured barbette carrying a single gun. Single layer controlling traverse & elevation by means of a joystick

Ammunition - fixed, cased round

Shell HE Mk 4T - Percussion fuze No. 251 or 255 and tracer-igniter in the base. Different tracers gave self-destruction at ranges of 3,400 or 5,500 yards
Shot AP Mk 6T - Plain steel shot with internal tracer

Propelling Charge
In brass case 12.25 inches long. For clipping into the charger it had a deep groove in the base.