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Type 4 30cm SP Mortar "Ha-To"

Referring to the world's largest self-propelled mortars, many people first think of the 2S4 "Tulip" 240mm self-propelled mortar that the Soviet Union equipped in 1975. Since the mortars had made great contributions to the Soviet army in the Great Patriotic War, the Soviet Union still attached great importance to this kind of artillery with a large amount of charge and curved ballistics after the war. In the 1970s, this kind of peaked artillery was launched. For example, the 3F-864 common grenade used in 2S4 has a weight of 130.84kg, far exceeding the 130 and 152 howitzer shells, not to mention the 228kg AMR-03F2 rocket range extender and nuclear shell with a range of 20km.

The Type 4 30cm SP Mortar "Ha-To" was developed in 1944. Ha-To had a Type 3 300mm Mortar, its weight of projectile was 170kg and the effective range was 3000m. Only 4 Ha-To were produced, and none of them were committed to combat.

As is known to all, the Japanese Army was a poorly armed army. It was limited by its own industry and technology. Japanese-made weapons are often very backward in performance. This is particularly serious in large-caliber siege guns. Although this effect was more or less diluted by the victory achieved during the Great War, it still faced these problems in the end. In the Pacific War, these contradictions eventually broke out and directly reflected in two siege wars that could affect the war situationthe Battle of Hong Kong and the Battle of Corregidor. Although the Japanese won, the losses were quite heavy. In addition to manpower and material resources, the most important thing is the loss of time. Corregidor fell in May 1942. If the Japanese military's siege guns performed better and the number was more, it can greatly speed up such sieges.

The Japanese army decided to develop a new type of siege gun at the end of 1942. This is a super-caliber mortar with a huge caliber of 300mm. It can launch 200kg shells two kilometers away. In Japan at that time, it was powerful. The greatest siege mortar. The artillery was successfully designed in the summer of 1943 and was named "Three-type 300mm heavy mortar." According to the test, the maximum range reached 3,145 meters, which greatly exceeded the design index, but on the other hand, the weight of the artillery reached three tons. Traditional mortar structures can cause deployment time to be very slow. Therefore, the original plan was modified, the artillery was modified from the traction type to the self-propelled type.

Towards the end of 1943 the Technical Office of the Japanese Army ordered the design of a vehicle that would make the support of artillery more mobile and immediate. With the aim of saving time and resources, already limited by the ongoing war effort, a 300 mm Type 3 heavy-duty mortar was planned to be installed on the hull of a tracked transport vehicle. The prototype was however finished only at the end of 1944 and handed over to the Imperial War Academy ; registered as "Type 4 Ha-To", it was immediately tested in the field: during the tests the new oneweapon system gave a good overall impression managing to shoot the bombs up to the maximum distance of 3,000 meters , despite the elevation could not go beyond 50 since the weight of 1 500 kilos of the mortar would have moved the center too far back of gravity of the crawler platform.

Defined by the military commission as an effective means, of the Type 4 was ordered a small series of additional three copies which was completed before the war ended. The four vehicles remained stationed on the home islands of Japan and none were used in battle. This choice was dictated by the cost of the single unit, considered too high by the controls, and by the encouraging developments recorded by the rocket launchers, which are also cheaper and faster to manufacture. The Type 4 design was then blocked at the experimental stage.

Sources disagree on the type of tracked selected. One reports that it was the Type 4 Chi-So troop carrier, driven by a 6- cylinder Mitsubishi diesel engine with 115 hp, equipped with a water cooling system. This vehicle could reach the maximum road speed of 40 km/h and had a maximum armor thickness of 25 mm; the rolling train consisted of seven wheels equipped with longitudinal swinging arm suspensions with helical springs: six were coupled and one was individually equipped. The reported total weight is 14.3 tons. A second source speaks instead of a "Chi-So" or "Chi-Ke" model artillery tractor, equipped with a 165 hp diesel engine at 2,000 rpm, equipped with 8 mm armor and a weight of 15 tonnes. It also reports the presence of a 7.7 mm Type 97 light machine gun.

The crew involved had seven men. The mortar placed in the back of the hull was a 300 mm Type 3: the piece was able to fire 170-pound bombs and had a maximum range of 3 000 meters, limited due to the aforementioned stability and safety problems.

The prototype was built at the end of 1944, and at the beginning of 1945 three pre-production machines were ready. By that time, the Japanese army already had 200 and 400-mm mortars. Compared to these simple designs, which were inexpensive to manufacture and fired from a simple wooden platform, the production of self-propelled mortars was considered to be prohibitively expensive. So the project was closed. After the surrender, one of these cars hit the Aberdeen testing ground.

Weight14.3 tons
Armor12 to 25 mm
Armament300mm mortar
Range74 miles
Engine115hp water cooled 6cyl Mitsubishi gasoline

Type 4 30cm SP Mortar Type 4 30cm SP Mortar Type 4 30cm SP Mortar

Type 4 30cm SP Mortar Type 4 30cm SP Mortar Type 4 30cm SP Mortar

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Page last modified: 14-06-2019 18:16:43 ZULU