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Type-98 10cm (4-inch)/65 caliber high angle gun

By far the most outstanding gun and mount used by the Japanese Navy was their 10cm (4-inch)/65 caliber Type 98 twin high angle gun mount. Turrets and ordinary type mounts were built; the former were fitted in the latest AA destroyer and the latter were used in AA batteries on land. The gun had a maximum range of 21,320 yards surface, and 14,220 yards vertical, with a rate of fire of 19°to 20 rounds per minute.

The 10cm Type 98 guns and mount were designed in 1938, in response to a demand for greater fire power in high angle guns. The 8cm mount is similar to the 10cm but on a smaller scale, and was designed mainly as as AA gun for the NAGANO class cruisers.

By using a 65 caliber gun, a range of 21,350 yards on the surface and 14,220 yards vertically was obtained with a rate of fire of 19-21 rounds per minute - a very great advance on any previous high angle gun built by the Japanese. Both the guns and the mounts, were undoubtedly the most out­standing of any around this size designed and built in Japan.

Fixed ammunition was used and supplied from the magazines to the working chambers in the fixed structure by two simple bucket tyne hoists, at the rate or 20-22 rounds per minute per hoist. In the working chamber the ammunition was man-handled from the top of the hoists to awaiting positions at the entrances to the gunloading pusher hoists.

There were two hoists built as one unit in each shipboard turret. The power supply for the hoists was independent of that for the remainder of the turret. Two hoists which are normal pusher type hoists, were interconnected and cannot work independently of each other. The hoists are controlled by a lever in the rear of the turret between the exit from the hoists. The speed of ammunition supply may be varied at will by suitably positioning the control lever. The maxim.um rate of supply was about 20-22 rounds per hoist per minute. On leaving the top of the hoist, the ammunition rolled automatically into one of the waiting positions from where it was passed to the loaders standing along­side the loading trays on platforms moving in elevation with the guns.

The loading trays, fuze setting machines and rammners were similar in principle to those of the 12.7cm. Type 89 mounts. The rammer was mounted above the guns instead of below as in the 12.7cm. gun and embodied certain improvements principally in the tripper gear, which had an improved type of tumbler release mechanism. In the early days of these mounts, frequent failures occurred due to fracturing of the rammer heads, but this trouble had been overcome and tne rammer was stated to be entirely satisfactory.

On rejection, the cartridge cases struck a large fixed def1ector and then dropped down a chute below the gunwell and through a door into the fixed structure around the bottom of the hoist, whence they were removed clear of the working chamber into spaces along the ship's side.

A normal recoil piston and cylinder was fitted above each gun and a runout spring below. Additional run-out springs (one per gun) are also fitted between and to the rear of the guns. The weight of the run-out springs, loading trays, and rammers is sufficient to balance the guns in elevation without the addition of special balance weights. The normal length of recoil is 19.3 inches and the trunnion height is 8.2 feet above the roller path.

In case of failure of power, the mount (including the hoists) can be left in operation entirely by hand. The main power motor is a 10 hp electric motor, which drives two "A" ends of a separate hydraulic system. supplying pressure to a "B" end for training the turret through normal worm and worm wheel.

A large number of documents or handbooks on many types of mounts, and a number of drawings, including a complete set of drawing of the 10cm Type 98 HA gun and mount, were sent to the United States from Sasebo Naval Gun Factory after the War. In destroyers NATSUZIKI and HANAZUKI it was hoped to see these mounts run under power, but, although the ships were less than a year old, the mounts had been so neglected since the end of the war that there was not time to put them in working condition before the ships sailed to repatriate Japanese nationals. Two mounts were, therefore, removed from NATSUZUKI and shipped to the United States.