 Erzherzog Ferdinand Max carried a primary armament of four 24 @-@ centimeter ( 9 @.@ 4 in ) / 40 caliber guns in two twin turrets on the centerline . These guns were an Austro @-@ Hungarian replica of the British 24 cm / 40 ( 9 @.@ 4 " ) <unk> C / 94 , which was used on the Habsburgs . Her secondary armament consisted of twelve 19 @-@ centimeter ( 7 @.@ 5 in ) / 42 caliber guns , also made by <unk> , mounted in eight single casemates on either wing of the ship and two twin turrets on the <unk> shell 20 @,@ 000 metres ( 22 @,@ 000 yd ) at maximum elevation with a muzzle velocity of 800 metres per second ( 2 @,@ 600 ft / s ) . The gun weighed 12 @.@ 1 tons and could fire three rounds per <unk> ships had a tertiary armament for protection against torpedo boats in the form of the 6 @.@ 6 centimetres ( 2 @.@ 6 in ) / 45 caliber gun , also manufactured by <unk> . Anti @-@ aircraft and airship protection was covered by the four 37 @-@ millimeter ( 1 @.@ 5 in ) Vickers anti @-@ aircraft guns on the ship bought from Britain in 1910 and mounted onto Erzherzog Karl . Erzherzog Ferdinand Max was also fitted with two above water 45 @-@ centimeter ( 17 @.@ 7 in ) torpedo tubes , although rarely used . 
