The first of the famous Bofors automatic guns placed into service, the 40 mm L/43 ubåtsautomatkanon Model 1932 (submarine automatic cannon) was developed from an early version of the Bofors 40 mm L/60 but with a shorter barrel and modified for submarine use. The gun and mounting was designed to be lowered into a water-proof tubular compartment under the decking for stowage. This was accomplished by elevating the gun to 90 degrees and then folding the fire-control handles and spent-cartridge chute up against the gun as can be seen in the photographs at right.

This weapon used the same ammunition as did the 40 mm L/60 gun but with a reduced propellant load.

Non-folding single and twin mounts were produced and exported to Poland, but the Royal Swedish Navy used only the single folding mount.

The last Swedish submarine armed with this gun was decommissioned in 1966.

Gun Characteristics

Designation 40 mm ubätsautomatkanon L/43 M/32
Ship Class Used On Sweden:
    Sjölejonet and Neptun classes

    Blyskawica 1

Date Of Design 1930
Date In Service 1932
Gun Weight 243 lbs. (110 kg)
Gun Length about 67.7 in (1.72 m)
Bore Length N/A
Rifling Length N/A
Grooves 16
Lands N/A
Twist Increasing RH twist
Chamber Volume N/A
Rate Of Fire 120 to 140 rounds per minute cyclic
80 to 90 rounds per minute practical
  • ^Six twin 40 mm mountings were delivered to Poland in 1937, at least two of which were 40 mm L/43 and the remainder 40mm L/60. The two 40 mm L/43 mountings were given to Blyskawica which carried them until rearmed in Britain with 40 mm L/60 guns in either 1940 or 1941. Other Polish ships were armed with Bofors guns including the minelayer Gryf and the submarines Orzel and Sep but it is not known if these were 40 mm L/43 or L/60 guns.


Type Fixed
Projectile Types and Weights AB 40 mm L/43 HE-T: 2.05 lbs. (0.93 kg) 1a 2a
Weight of Complete Round about 4.41 lbs. (2.0 kg)
Bursting Charge HE-T: about 0.150 lbs. (0.068 kg) TNT
Projectile Length 7.25 in (18.4 cm)
Complete Round Length 17.60 in (44.7 cm)
Cartridge Case Type, Size and Empty Weight Brass, 40 x 311R, 1.93 lbs. (0.88 kg)
Propellant Charge 0.485 lbs. (0.220 kg)
Muzzle Velocity 2,297 fps (700 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
  • ^As noted above, this weapon used the same ammunition as produced for the Bofors 40 mm/60 but with a reduced propellant charge. Rounds were self-destructing.
  • ^Similar to the ammunition for the 40 mm L/60, ammunition was supplied in 4-round clips and the autoloader normally held two clips.


Range with 4.41 lbs. (2.0 kg) HE-T
Elevation Distance
Max Horizontal Range
about 4,800 yards (4,370 m)
Max Possible Horizontal Range
(no self-destruct)
about 10,900 yards (9,980 m)
Max Vertical Range
about 14,650 feet (4,460 m)

Mount/Turret Data

Designation Sweden Single Folding Mounts: Sjölejonet (2) and Neptun (1): N/A

Poland Twin non-Folding Mounts: Blyskawica (2): 40 mm L/43 Model 1937

Weight Single Mount: about 1,984 lbs. (900 kg)
Twin Mount: 6,173 lbs. (2,800 kg)
Elevation -10 to +90 degrees
Elevation Rate N/A
Train 360 degrees
Train Rate N/A
Gun recoil N/A

Additional Pictures


"The Bofors Gun" by Terry J. Gander

Page History

30 December 2017 - New datapage
05 March 2018 - Converted to HTML 5 format and added photograph of Polish guns