 The ships were also armed with a secondary battery of sixteen 15 cm ( 5 @.@ 9 in ) SK L / 45 quick @-@ firing guns , each mounted in MPL C / 13 casemates in the side of the top deck . These guns were intended for defense against torpedo boats , and were supplied with a total of 2 @,@ 240 shells . The guns could engage targets out to 13 @,@ 500 m , and after improvements in 1915 , their range was extended to 16 @,@ 800 m . The guns had a sustained rate of fire of 5 to 7 rounds per minute . The shells were 45 @.@ 3 kg ( 99 @.@ 8 lb ) , and were loaded with a 13 @.@ 7 kg ( 31 @.@ 2 lb ) RPC / 12 propellant charge in a brass cartridge . The guns fired at a muzzle velocity of 835 meters per second ( 2 @,@ 740 ft / s ) . The guns were expected to fire around 1 @,@ 400 shells before they needed to be replaced . 
