The 20.3 cm SK C/34 was the main battery gun used on all German World War II heavy cruisers.
These built-up guns consisted of a rifled tube encased within an inner and outer jacket with a horizontal sliding breech block. The breech was sealed with an 18 kg (40 lb) brass case containing 30 kg (66 lb) of smokeless powder with a 160 gram (5.6 oz) gunpowder igniter. A cloth bag containing an additional 21 kg (40 lb) of smokeless powder and 380 grams (13 oz) of gunpowder was loaded between the projectile and the brass case. Each gun could fire approximately five rounds per minute. Useful life expectancy was 510 effective full charges (EFC) per barrel.