The primary armament consisted of a dozen 40-caliber 12.7 cm Type 89 anti-aircraft (AA) guns in twin mounts on sponsons along the sides of the hull. They fired projectiles at a rate between 8 and 14 rounds per minute at a muzzle velocity of ; at 45°, this provided a maximum range of , and a maximum ceiling of . The ships were also initially equipped with eight triple 25 mm Type 96 light AA guns alongside the flight deck. They fired projectiles at a muzzle velocity of ; this provided a maximum range of , and an effective ceiling of at +85°. The maximum effective rate of fire was only between 110 and 120 rounds per minute due to the frequent need to change the fifteen-round magazines. In mid-1943, four more triple mounts were added and another four triple mounts in late 1943–early 1944. Two of these last four mounts were mounted on the stern and the others were placed in front of and behind the island. A dozen single mounts were also added, some of which were portable and could be mounted on tie-down points on the flight deck. After the Battle of the Philippine Sea in June 1944, "Jun'yō"s anti-aircraft armament was reinforced with three more triple mounts, two twin mounts and 18 single mounts for the 25 mm Type 96 gun. These guns were supplemented by six 28-round AA rocket launchers. Each rocket weighed and had a maximum velocity of . Their maximum range was . In October 1944, "Jun'yō" had a total of 91 25 mm barrels; 57 in 19 triple mounts, four in two twin mounts, and 30 single mounts.