12 . 7 cm / 50 Type 3 naval gun The 12 . 7 cm / 50 Type 3 naval gun was a medium calibre naval gun of the Imperial Japanese Navy used during World War II . It was the standard weapon for Japanese destroyer s between 1928 and 1940 . It has been credited as a true dual - purpose gun , but this was more a nominal capability than real as its bag propellant and need for hand ramming required the gun to be loaded at angles between 5 – 10° which dropped its rate of fire to a relatively slow 5 – 10 rounds per minute and its training speed of only 6° per second meant that it had a great deal of difficulty engaging enemy aircraft with any chance of success . After the end of World War II the gun remained in service on the two Japanese destroyers ceded to the Soviet Union and the Republic of China as war reparations , the last of which was scrapped in 1970 after running aground in a typhoon . Description . The 50 caliber " Type 3 " gun was " of built - up construction , originally with three and later two layers with the usual breech ring and breech bush . " It used a Welin interrupted screw breech . The shell was fuzed manually on the loading tray before being rammed by hand and could only be loaded at elevations between 5° and 10° . All mounts used pusher type shell hoists , but the powder bags were passed by hand . Mountings . These guns were first used in the twin gun " Model A " turret on the revolutionary " Fubuki " - class destroyers . These were the first weatherproof , splinterproof and gas - proof enclosed gun turret s ever mounted on a destroyer . Guns in twin mounts were in individual cradles and could elevate separately . All twin gun mounts weighed approximately . All mounts could traverse at 6° per second and could elevate at a rate between 6° and 12° per second although speeds up to 27° per second have been reported . The twin gun " Model A " mount was fitted with a thick gun shield . Its guns could depress −5° and elevate to + 40° . These mounts were deployed on the first ten " Fubuki " - class destroyers . The twin gun " Model B " mount had its elevation increased to 75° and was fitted in the rest of the " Fubuki " - class as well as the " Akatsuki " - class destroyers . In order to save weight its gun shield was reduced to in thickness , but this proved too thin to withstand heavy seas and was later reinforced . The first four " Hatsuharu " - class s used the " Model B mod 2 " mount although how it differed from the earlier " Model B " mount is unknown . The last two of the " Hatsuharu " - class , the " Shiratsuyu " - class , the " Asashio " - class , and the " Kagerō " - class destroyers used the " Model C " which reduced its maximum elevation to 55° , but could depress to −7° and was supposedly lighter than earlier models The " Model D " used by the " Yūgumo " - class and the " Shimakaze " destroyers retained the depression limit of the " Model C " , but elevation returned to the 75° of the " Model B " . The " Type A " single mount could depress −7° and elevate to + 75° , but the " Type B " reduced the maximum elevation to 55° . Both mounts weighed approximately . The " Type A " was fitted on the " Hatsuharu " - class and the " Type B " on the " Shiratsuyu " - class destroyers . Ammunition . The gun normally fired a high - explosive shell , an illumination shell or an incendiary shrapnel round ( " sankaidan " ) intended for anti - aircraft use . All of these shells weighed and used of " 30 DC " propellant . After 1943 , a flat - nosed anti - submarine shell also became available . This had a minimum range of and a maximum range of . An new , heavier , but more streamlined , high - explosive projectile with a range of was under development when the war ended .