The "Colossus" class was equipped with ten 50-calibre breech-loading (BL) Mark XI guns in five hydraulically powered twin-gun turrets, three along the centreline and the remaining two as wing turrets. The centreline turrets were designated 'A', 'X' and 'Y', from front to rear, and the port and starboard wing turrets were 'P' and 'Q' respectively. The guns had a maximum elevation of +20° which gave them a range of . They fired projectiles at a muzzle velocity of at a rate of two rounds per minute. The ships carried 100 shells per gun.