 The 2 @-@ pounders were replaced in 1939 by 20 license @-@ built Hotchkiss 25 @-@ millimeter Type 96 light AA guns in a mixture of twin @-@ gun and single mounts . This was the standard Japanese light AA gun during World War II , but it suffered from severe design shortcomings that rendered it a largely ineffective weapon . According to historian Mark Stille , the twin and triple mounts " lacked sufficient speed in train or elevation ; the gun sights were unable to handle fast targets ; the gun exhibited excessive vibration ; the magazine was too small , and , finally , the gun produced excessive muzzle blast " . These 25 @-@ millimeter ( 0 @.@ 98 in ) guns had an effective range of 1 @,@ 500 – 3 @,@ 000 meters ( 1 @,@ 600 – 3 @,@ 300 yd ) . The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the 15 @-@ round magazines . As far as is known , no additional AA guns were installed aboard Mutsu before her loss . Additional 25 @-@ millimeter guns were installed aboard Nagato during the war ; on 10 July 1944 , she was reported to have 98 guns on board . An additional 30 guns were added during a refit in Yokosuka in November . Two more twin 127 @-@ millimeter gun mounts were added at the same time abreast the funnel and all of her 14 @-@ centimeter guns were removed as she was now a floating anti @-@ aircraft battery . 
