Designed to arm commerce-raiding heavy cruisers and for coastal defense, a single prototype was built but this weapon did not enter service use.

Actual barrel length was 55.74 calibers. Actual bore diameter was 30.50 cm (12.008").

Gun Characteristics

Designation 30.5 cm/56 (12") SK C/39
Ship Class Used On Planned
Date Of Design 1939
Date In Service Not in service
Gun Weight 147,267 lbs. (66,800 kg)
Gun Length oa 669.29 in (17.000 m)
Bore Length 626.97 in (15.925 m)
Rifling Length 500.98 in (12.725 m)
Grooves (72) 0.142 deep x 0.319 (breech) - 0.3425 in (muzzle) (3.6 deep x 8.11 to 8.70 mm)
Lands 0.205 (breech) to 0.1815 in (muzzle) (5.20 to 4.61 mm)
Twist Increasing RH 1 in 32.6 to 1 in 27.6
Chamber Volume 17.697 in3 (290 dm3)
Rate Of Fire 2 - 3 rounds per minute


Type Cartridge - Bag
Projectile Types and Weights 1 APC L/4,9: 915 lbs. (415 kg)
HE L3,8 base fuze: 915 lbs. (415 kg)
HE L/3,6 base and nose fuze: 551 lbs. (250 kg)
Bursting Charge APC L/4,9: N/A
HE L/3,8 base fuze: N/A
HE L/3,6 base and nose fuze: 32.0 lbs. (14.5 kg)
Projectile Length APC L/4,9: 58.8 in (149.5 cm)
HE L/3,8 base fuze: 45.6 in (115.9 cm)
HE L/3,6 base and nose fuze: 55.1 in (140 cm)
Propellant Charge APC and HE: 379 lbs. (172 kg) RP C/40N
Coastal HE: 441 lbs. (200 kg) RP C/40N
Muzzle Velocity APC: 2,880 fps (865 mps)
HE: 2,880 fps (865 mps)
Coastal HE: 3,675 fps (1,120 mps)
Working Pressure For APC L/4,9: 19.0 tons/in2 (3,000 kg/cm2)
For HE L/3,6 base and nose fuze: 21.0 tons/in2 (3,300 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
  • ^It is believed that this gun would have used the same projectiles as used for the older 30.5 cm/50 guns.


Range with 915 lbs. (415 kg) APC for coastal artillery
Elevation Distance
49.0 degrees about 46,800 yards (42,800 m)
Range with 551 lbs. (250 kg) Coastal HE L/3,6 Shell for coastal artillery
Elevation Distance
49.1 degrees (?) 56,200 yards (51,400 m)

The APC L/4,9 shell had a significantly better ballistic shape than the previous projectiles. It is noted as being "of longer range" than the older APC, which I take to mean that the newer projectile would have had a longer range when fired at the same elevation.

Mount/Turret Data

Designation N/A
Weight N/A
Elevation N/A
Elevation Rate N/A
Train N/A
Train Rate N/A
Gun recoil N/A
Loading Angle N/A


"Naval Weapons of World War Two" by John Campbell

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