 Four 3 " / 23 caliber Mark 11 anti @-@ aircraft guns were planned for the original and first redesigned versions of the Lexingtons . This was increased to eight guns in the final version . These could depress to − 10 degrees and elevate to 85 degrees . They fired a 13 @-@ pound ( 5 @.@ 9 kg ) shell at a muzzle velocity of 1 @,@ 650 fps ( 503 mps ) and rate of between eight and nine rounds per minute to a range of 8 @,@ 800 yards ( 8 @,@ 000 m ) and a height of 18 @,@ 000 feet ( 5 @,@ 500 m ) . 
