The guns mounted on the Admiral Graf Spee were used triple-barreled, meaning there was three 283mm guns on each turret, making 6 in total, three guns on two turrets. During World War II, the 283mm guns in Deutschland-class was later improved to 28cm SK C/34 Naval gun in 1934 on Scharnhorst-class ships.
Its effective firing range was 12.42 miles (20km) and its maximum range was up to 22.68 miles (36.5km). Each of the shells shot by the 283mm guns weighed in 300kg. Each gun weighed in about 48 tons. It's rate of fire was up to 2.6 rounds per minute. It's maximum muzzle velocity is around 360 m/s (1,181 ft/s).
Source : Myself, Wikipedia.
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