Type 96 25 mm AT / AA Gun The was an automatic cannon used by the Imperial Japanese Navy during World War II . A local built variant of the French Hotchkiss 25mm anti - aircraft gun , it was primarily used as an anti - aircraft gun in fixed mounts with between one and three guns , but was designed as a dual - purpose weapon for use against armored vehicles as well . History and development . In 1935 the Imperial Japanese Navy decided to replace the earlier 40 mm Vickers " pom - pom " gun s with a 25 mm Hotchkiss design . A party of Japanese officers and engineers traveled to France to evaluate the design in 1935 and an order was placed for a number of guns and mounts for evaluation . Firing tests of these guns were conducted at Yokosuka Naval Arsenal in 1935 . The first few weapons were built in France under the designation “ Type 94 ” and “ Type 95 ” , with the mass production model produced at the Yokosuka Arsenal being designated “ Type 96 ” . The Japanese made a number of minor changes to the original Hotchkiss design and production process , changing some components from forgings to castings to simplify production and replacing the simple conical flash suppressor with a Rheinmetall - type design . A submarine - mountable version of the gun was also produced , which made extensive use of stainless steel . The double mount type was the first to enter service , with triple mounts following in 1941 and finally single mounts later in 1943 . Design . The Type 96 25mm Gun is a simple air - cooled gas operated design . The barrel is a forging screwed into the breech mechanism . Additional support is provided to the breech end of the gun barrel by the finned cooling jacket . The barrel is changeable , but the operation required two men and special tools to complete , and took a trained crew approximately five minutes . By adjusting the gas valve setting it was possible to vary the rate of fire between 200 and 260 rounds per minute , with 220 rounds per minute being the standard setting . The gun mounts were normally provided with one of three gun sight s : Land mountings and all single mountings all used the single open ring sight . The Type 95 sight was used on ship - based multiple mounts , in the case where the mount has a powered drive linked to a fire director it was used as a backup . The Type 95 sight was originally designed with a maximum target speed of 600 kilometers per hour ; however , experience showed that aircraft often exceeded this speed . To compensate for the problem a ring was added to the sighting telescope to provide an additional offset for the speeds up to 900 kilometers per hour . The gun was normally used without a gun shield , although some multiple mounts on " Yamato " - class battleship s were fitted with a Ducol ( High tensile steel ) shields . Many ship based mounts also had splinter shields . Effectiveness . In interviews conducted by the U . S . Naval Technical Mission to Japan after the end of the war , Japanese military personnel cited it as the most reliable Japanese anti - aircraft weapon , but second in effectiveness to the Type 98 100 mm anti - aircraft gun . The Type 96 was most effective when used at ranges of 1 , 000 meters or less . Japanese military estimated that it required an average of 1 , 500 rounds to down an aircraft at a height of 1 , 000 meters and a range of 2 , 000 meters and that fire beyond that range was completely ineffective . Later in the war when ammunition supply was restricted , firing was held until the targets were within 800 meters range this dropped to a low as seven rounds per aircraft according to Japanese sources . The Japanese ranked in order of seriousness the problems with the gun as : In " Rapid Fire " , Anthony Williams writes that the intermediate calibre weapons ( including the US Navy ' s 1 . 1 " / 75 caliber gun " ) were relatively unsuccessful during World War II , the mounts were much heavier and more complex , but the shells lacked the range and hitting power of the larger 37 and 40 millimeter mounts . Certainly the Japanese ranked increasing the caliber of autocannons as the number one priority of research and development Variants . Ammunition . The Type 96 cartridge case was a rimless type design with a deep extraction groove at the base . The projectiles fired by the weapon were slightly unusual in that they had two rotating band s . The forward band was slightly smaller in diameter than the rear band . It was believed that this was to reduce wear on the rifling near the chamber . The case of the cartridge was crimped around the rear rotating band . The complete round weighed approximately with the projectile weighing . The propellant was 102 grams of single - perforated , graphited grains of nitrocellulose approximately 2 millimeters in diameter and between 2 . 5 and 4 . 5 millimeters in length . Normally one tracer round was added every four or five rounds to aid laying . Combat record . The Type 96 was the standard Japanese medium antiaircraft weapon the Imperial Japanese Navy , being mounted aboard practically everything that floated , and was also used in land bases in the Japanese Empire and in the Japanese overseas combat fronts . These weapons were also used as anti - tank gun s in some defensive actions in Pacific theaters and against land objectives in southeast Asia / Chinese mainland during the Pacific War .