30 . 5 cm SK L / 50 gun The 30 . 5 cm SK L / 50 gun was a heavy gun mounted on 16 of the 26 German capital ships built shortly before World War I . The gun , firing a shell slightly greater than 12 inches in diameter , was designed in 1908 , and entered service in 1911 , when the four s — the first ships to carry the weapons — were commissioned into the High Seas Fleet . It was also mounted on the five subsequent and four s , as well as the three s . The guns were used to great effect at the Battle of Jutland on 31 May – 1 June 1916 , when the two " Derfflinger " - class ships , and , used them to destroy the British battlecruisers and . The gun was eventually superseded in German naval use by the much larger and more powerful 38 cm SK L / 45 . Before World War I , 30 . 5 cm SK L / 50 guns were emplaced on the islands of Helgoland and Wangerooge to defend Germany ' s North Sea coast . One battery was emplaced during the war to defend the port of Zeebrugge in Occupied Flanders . The guns on Helgoland were destroyed by the victorious Allies at the end of the war , but the battery at Wangerooge survived intact . Three of its guns were transferred to Helgoland after the island was remilitarized in 1935 . During the Second World War , the other three guns were transferred to France and employed in coastal defense positions along the English Channel . Specifications . Naval Turrets . These guns were mounted in twin gun turrets in each of the ships on which they were carried . The " Helgoland " - class ships used six Drh LC / 1908 mountings ; these turrets had - thick roofs and - thick sides . Later ship classes used improved designs . The " Kaiser " class carried five Drh LC / 1909 gun houses , while the subsequent " König " class carried five turrets of the Drh LC / 1911 type . The primary improvement for the LC / 1909 turret was an increase in armor thickness of the roof , from 100 mm to ; side armor remained the same . The turret roofs on the LC / 1911 mounts were reduced to ; again , the sides remained at a thickness of 300 mm . " Derfflinger " and " Lützow " used four Drh LC / 1912 mountings , while their half sister carried an improved Drh LC / 1913 type . The LC / 1912 mounts had 110 mm - thick roofs and 270 mm - thick sides . The turrets on the newer " Hindenburg " had the thickness of their roofs increased to , though the sides were the same as in the preceding LC / 1912 type . Weights for the gun houses ranged from 534 – 549 tons ( 543 – 558 metric tons ) ; the variations depended primarily on the thickness of armor . In the " König " - class ships , each gun turret had a working chamber beneath it that was connected to a revolving ammunition hoist leading down to the magazine below . The turrets were electrically controlled , though the guns were elevated hydraulically . In an effort to reduce the possibility of a fire , everything in the turret was constructed of steel . This layout was also used in the preceding battleships . On the " Derfflinger " - class battlecruisers , the two forward and the superfiring rear turret used this configuration , although the rearmost gun turret had its magazine and shell room inverted . All of the German gun turrets initially allowed for elevation to 13 . 5 degrees , although after the battle of Jutland , they were modified to allow elevation to 16 degrees . The centerline turrets on the warships could train 150 degrees in either direction , though the wing turrets on the " Helgoland " and " Kaiser " classes were limited to an arc of 80 degrees in either direction . Coast defense mounts . The island of Helgoland received four twin gun turrets between 1909 – 12 , although their exact type is unknown . Battery Kaiser Wilhelm II was built to protect the port of Zeebrugge in Occupied Flanders during World War I . It consisted of four guns in concrete barbettes mounted on " Bettungsschiessgerüst ( BSG ) " ( firing platforms ) . These manually powered mounts rotated on a pivot at the front of the mount and the rear was supported by rollers resting on a semi - circular rail . They were equipped with a gun shield and capable of all - around fire . They were manned by sailors from Naval Artillery Regiment ( " Matrosen Artillerie Regiment " ) 1 . By the end of World War I , six guns in BSG mounts equipped Battery Friedrich August on the island of Wangerooge . Three of these were transferred to Helgoland after 1935 when Hitler renounced the Treaty of Versailles which had demilitarized the island . By 1938 , they equipped Battery von Schröder and were manned by troops of the Second Naval Artillery Battalion ( " II . Marine - Artillerie - Abteilung " ) , later 122nd Naval Artillery Battalion ( " 122 . Marine - Artillerie - Abteilung " ) . After the French were defeated in 1940 all three guns were transferred to Le Trésorerie , near Boulogne - sur - Mer , France where they assumed their former name of Battery Friedrich August . These guns were initially in open barbettes with 360° traverse , but these were later rebuilt into concrete casemate s with overhead cover . that could elevate to 50 degrees and train 220 degrees in either direction . Ammunition . These guns fired two types of shells during World War I : armor - piercing ( AP ) L / 3 . 1 and high explosive ( HE ) L / 4 types . During World War II , the guns fired a wider variety of shells , including armor - piercing L / 3 , 4 and L / 4 , 9 types , and high explosive L / 3 . 8 , L / 5 , and L / 4 . 8 shells , as well as specially designed coast defense artillery projectiles . The AP and HE rounds weighed between 405 and 415 kg ( 915 lb ) , while the coastal artillery projectiles weighed only 250 kg ( 551 lb ) . Shells used during World War I used an RP C / 12 main propellant charge that weighed 91 kg ( 201 lb ) and a smaller RP C / 12 fore charge that weighed 34 . 5 kg ( 76 lb ) ; this gave the guns a muzzle velocity of 855 meters per second ( 2 , 805 feet per second ) . Coast defense guns used RP C / 32 charges that weighed 85 . 4 kg ( 188 . 3 lb ) for the main charge and 41 . 6 kg ( 91 . 7 lb ) for the fore charge . After 1942 , these were increased to 121 . 5 kg ( 268 lb ) RP C / 38 for AP shells and 143 kg ( 315 lb ) RP C / 38 for HE rounds . These shells were fired with a muzzle velocity of between 850 – 855 m / s ( 2 , 789 – 2 , 805 ft / s ) , but the lightweight coast defense shell had a muzzle velocity of 1 , 120 m / s ( 3 , 700 ft / s ) . Performance . At 13 . 5 degrees of elevation , the 30 . 5 cm gun could hit targets out to 16 , 200 m ( 17 , 717 yards ) with armor - piercing shells . After the turrets were improved to allow elevation to 16 degrees , the range correspondingly increased to 20 , 400 m ( 22 , 310 yd ) . At a range of 12 , 800 m ( 14 , 000 yd ) , the L3 armor - piercing shells fired by the gun were expected to penetrate 254 mm ( 10 in ) of armor plate . At 15 , 000 m ( 16 , 000 yd ) the effectiveness of the shell decreased ; it was able to pierce 229 mm ( 9 in ) - thick plate . The range of the World War II guns was significantly greater than the guns used in World War I . With the 405 kg shell at 45 degrees , the guns had a maximum range of 32 , 000 m ( 35 , 000 yd ) . With the 415 kg shell at 49 . 2 degrees , the range was 41 , 300 m ( 45 , 166 yd ) , and with the lighter 250 kg round at 49 . 1 degrees , the maximum range was 51 , 400 m ( 56 , 200 yd ) .