 Light AA defense was handled by ten quadruple , water @-@ cooled , 46 @-@ K mounts fitted with 37 mm ( 1 @.@ 5 in ) 70 @-@ K guns with 1800 rounds per gun . Initially only eight mounts were planned when the ships began construction , but two more were added later , probably in January 1941 , one on each side of the forward superstructure . Each mount was fully enclosed to protect the crew from the muzzle blast of the larger guns and against splinters . The guns fired <unk> @-@ kilogram ( 1 @.@ 61 lb ) shells at a muzzle velocity of 880 m / s ( 2 @,@ 900 ft / s ) . Their effective anti @-@ aircraft range was 4 @,@ 000 meters ( 13 @,@ 123 ft ) . 
