Canon de 138 mm Modèle 1929 The Canon de 138 mm Modèle 1929 was a medium calibre naval gun of the French Navy used during World War II . It was used on the large destroyers ( " contre - torpilleurs " ) of the " Fantasque " and " Mogador " classes . Description . The 50 - caliber " Mle 1929 " was a lengthened version of the Modèle 1927 . It used the semi - automatic action of the older gun as well as its horizontal sliding block breech . It had an autofretted monobloc barrel as well . It weighed , but the later " Modèle 1934 " weighed for some reason , but appears to have been otherwise identical . Mountings . Modèle 1929 . The " Mle 1929 " gun was used in single , hand - worked and trained , center - pivot mountings that weighed approximately that were fitted with a thick gun shield . The mount could depress - 10° and elevate to + 30° , which gave it a maximum range of . Ammunition was brought up to the handling room by hoist from the magazines . From there the shells were transferred to the " guttering " ( " gouttières " ) which encircled the mount and allowed the shells to line up with the gun ' s breech regardless of the gun ' s angle of bearing . Powder cartridges were fed into similar center - line chutes . The gun had a nominal firing cycle of 4 or 5 seconds with its automatic spring rammer , but the dredger hoists transporting the shells and cartridge cases slowed the rate of fire down to 7 rounds per minute . This gun was only used on the large destroyers ( " contre - torpilleurs " ) of the " Fantasque " class . Modèle 1934 . The " Mle 1934 " gun was installed in twin - gun , electrically powered Modèle 1934 base - ring " pseudo - turrets " that weighed that were fitted with a thick , open - backed gunhouse . These were mounted on the large destroyers ( " contre - torpilleurs " ) of the " Mogador " class . The guns were housed in separate cradles that could be coupled together and could elevate to a maximum of 30° and depress 10° . The underpowered electric motors gave a maximum training speed of 10° per second and a maximum elevating speed of 14° per second . They were initially installed within the mountings , but were moved to the outer sides of the turrets to free up room . The pusher - type ammunition hoists ran up a fixed shaft in the center of the mount . The shells and their powder charges were transferred to a tipping drum that was rotated to match the bearing angle of the guns and then loaded . This system was adapted from that used for the fixed ammunition used in the " Le Hardi " class destroyers . Unfortunately it was not well suited for separate - loading ammunition . Each gun had its own separate shell and powder hoist , for a total of four hoists . The tipping drum had four matching separate trays to move the ammunition to the gun . Each shell was power - rammed , but the propellant charges had to be hand - rammed . Theoretically the guns could be loaded at any angle , but the power rammer was so weak that it could not ram shells at angles above 10° . This problem , coupled with the " poor quality of manufacture of the guns , the unsatisfactory profile of the breech , resulted in a firing cycle of only 3 - 4 rounds per minute during the early trials with jams and failures frequent " , rather than the planned 10 rounds per minute . A further problem was that there only two loaders assigned to the gun crew ; they tired quickly during prolonged firing . Gunnery trials were conducted when " Volta " was on her sea trials in mid - 1939 and were " an unmitigated disaster " for the reasons given above . Some fixes were identified , notably modifications to the breech , installation of split loading trays and reinforcement of the catapult rammers , but they had to wait until the ships ' next refit to be implemented . But even these modifications were only stop gaps and an entirely new loading system was deemed necessary , but since this was expected to take 10 – 12 months to develop the current system would have to be used . Both " Volta " and " Mogador " were refitted in January 1940 and had their turrets modified , although loading still could not be done at angles higher than 10° . The surrender of France in June 1940 ended any work on a new loading system . Five - round ready racks for each gun were added to the sides of the turrets during the refit to compensate for any problems with the loading systems . Ammunition . The " Mle 29 " and " Mle 34 " primarily used two different shells , each propelled by of " BM 11 " in a separate brass cartridge case . Beginning in January 1940 " OPFK " shells with dye markers were carried . These were intended to allow each ship to distinguish between its shell - bursts and those of other ships by use of coloured dyes . An illumination shell was also used , but details are unknown .