Military Review

Japanese aircraft gun Ho-301

In 1944, a new heavy bomber appeared on the Pacific theater of the Second World War. The characteristics of the Boeing B-29 Superfortress allowed it to effectively strike at enemy ground targets. A characteristic feature of the B-29 was also powerful defensive weapons. 12 machine guns of caliber 12,7 millimeters made an attempt to bring down a bomber very challenging. In this regard, the Japanese designers have attempted to create a new weapon for fighters, able to effectively deal with the new American bomber.

Japanese aircraft gun Ho-301

The Ho-301 project implied the creation of an automatic gun of 40 millimeters caliber, suitable for use on existing fighters. To ensure all the requirements, especially weight, it was necessary to apply the original and non-standard for aviation technical solution at that time. In accordance with the plans of Japanese designers, the gun Ho-301 was to use a new shell of the original design.

Externally, the 40-mm projectile looked like a cylinder and had a tapered nose. It housed a pin fuse. The total length of the projectile was equal to 129 mm, and the weight - 585 g. Immediately after the fuse in the projectile placed a large amount of explosives. 65 grams of TNT or other suitable explosive could be placed in the cavity. The fuse and volume with charge occupied about two thirds of the total length of the projectile. Behind them was the chamber of the propellant charge. A propellant mass of 10 g in a small silk bag was placed inside this cavity and covered with a thin aluminum plate. On top of the latter, the bottom with 12 holes, which played the role of nozzles, was screwed into the shell of the shell. Between the nozzles in the center of the Donets, located primer.

The original design 40-millimeter projectile allowed significantly simplify the design of the gun itself. Applied ideas made it possible to abandon several mechanisms and details related to the sending of a projectile into the barrel of the gun and the extraction of spent cartridges. When firing, the drummer of the cannon hit the primer that ignited the propellant charge. After the pressure in the chamber reached a certain value, the aluminum plate burst, and the powder gases burst out through the nozzles in the bottom. The propellant charge was calculated in such a way that it managed to completely burn before the projectile left the gun. Due to the absence of a separate cartridge with a propelling charge that needs to be removed and thrown away after the shot, the Ho-301 cannon can be classified as a bagless weapon.

The gun itself had a relatively simple design. The shells were fed to the line of dropping from the box magazine for ten shells, which was above the receiver. It is noteworthy that this design of the store allowed it to be positioned on both sides of the gun without additional modifications of any mechanisms. Automation worked on the principle of a free shutter with advanced ignition caps. This Japanese gun Ho-301 recalls some of the development of the Swiss company Oerlikon. The gun with a total length of 148 centimeters (barrel length - 78 cm) weighed 89 kg. Such parameters made it possible to install two similar weapons on fighters at once.

Using the proven principle of operation of the automatics with the new projectile yielded interesting, although ambiguous results. First of all, it is necessary to note a fairly high rate of fire - up to 475 shots per minute. Automatic guns of that time, which had a similar caliber, due to the use of "traditional" ammunition with a sleeve had a noticeably lower rate of fire. For example, the Swedish 40-mm cannon Bofors L60 had a rate of fire about 120 rounds per minute.

The high rate of fire of the new Japanese gun Ho-301 allowed to hope for its great prospects, but the use of the original bezgolzovogo ammunition led to dubious firing characteristics. A ten-gram throwing charge dispersed a projectile with a mass of 585 g to a speed of just 245 meters per second. It is not difficult to guess what the ballistics of such ammunition was. The characteristics of the Ho-301 cannon allowed to fight effectively only with heavy bombers who could not actively maneuver while moving away from the attack. At the same time, the effective firing range did not exceed 150-180 meters.

Despite the obviously low performance, the Ho-301 gun was mass-produced. The horizontal placement of the box magazine above the receiver made it possible to install new weapons in the wings of fighters. Ho-301 guns were limitedly used on the Nakajima Ki-44 and Kawasaki Ki-45 fighters, two per plane. The results of the use of new caseless tools in practice proved to be mixed. For a successful attack, the fighter pilot had to approach the target for a very small distance. At distances of no more than 150-200 meters, a Japanese aircraft was at great risk of being shot down or at least seriously damaged. Unsuccessful characteristics of guns and small ammunition - all 20 shells did not allow attacking from long distances.

Nevertheless, a well-constructed approach to an enemy aircraft and accurate shooting led to stunning results. The 65-gram explosive charge and a crushing weighing about 500 grams literally ripped apart the design of an enemy plane into pieces. One precise hit was enough to disable the engine or destroy important structural elements. But, as can be seen from the characteristics of the gun, such successful attacks were rare. More often, Japanese fighter pilots had to retreat and launch a new attack, trying not to fall back.

A small number of Ho-301 cannons and specific characteristics prevented them from having a noticeable impact on the air war over the Pacific Ocean. Moreover, the Japanese pilots, assessing the real possibilities of an automatic cannon with a bezgilzovym projectile, eventually abandoned it. Ho-301 guns were gradually dismantled from the fighters, and in their place large-caliber machine guns were installed. With a much smaller power of bullets, such a weapon had a greater rate of fire and a significant ammunition, which in practice compensated for the insufficient destructive effect.

A number of Ho-301 automatic cannons were used by Japanese pilots in Burma almost to the very end of the war. Aircraft armed with 40-millimeter cannons were used as attack aircraft. The ground attack features made it possible to fire Ho-301 cannons with markedly greater efficiency compared to air combat, and the power of projectiles had a good effect on the results of air strikes.

However, no guns with original ammunition and other interesting technical or tactical decisions could affect the course of the war. The superiority of the American and then the Soviet armed forces did their job. In early September, 1945, Japan capitulated and all the development of its own weapons, including aircraft guns, temporarily stopped.

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  1. fzr1000
    fzr1000 11 September 2013 08: 46
    The Japanese, as always, do not go the beaten path. Oh well.
    1. luiswoo
      luiswoo 11 September 2013 14: 45
      Quote: fzr1000
      The Japanese, as always, do not go the beaten path. Oh well.

      Unfortunately for us, this idea was not the first to come to them, back in the 30's, Yakov Grigorievich Taubin developed the 40mm AG-TB, which, among other things, was planned to be used in aviation (I do not understand why the Ho-301 is called a "cannon", although its "shell" is a pure grenade) In general, Taubin was shot and the project stalled.
  2. AlexVas44
    AlexVas44 11 September 2013 09: 03
    The idea is interesting. And what was it worth to increase the propellant charge?
    1. Rus86
      Rus86 11 September 2013 09: 52
      besides the increased power of bestowal, probably so many problems would have surfaced. as an example, a wonderful aircraft gun, ours, of Soviet design, gsh-6-30, the arode is called so, so there, with a queue length of more than 10 shots, it broke the mounts, disrupted the operation of sights, etc. although the power of the volley was and is beyond.
      1. Taoist
        Taoist 11 September 2013 12: 40
        Well, the impact of GSN 6-30 was certainly great but by no means beyond. VYA 23 (which was put on Il2) had a similar return. Recoil is always the inverse of the mass and velocity of the projectile.
        Apparently, the Japanese simply did not manage to create a sanely working automation for a powerful cartridge - as a result, they ended up with an undershot and a reloading launcher. And taking into account the fact that this miracle had ammunition loading, then in general its meaning as an aircraft weapon became doubtful. Yes, and the projectile, due to the need to enter into it, and the propellant charge is not impressive. The same Soviet NS 45 used a 45mm anti-tank gun shell weighing more than a kilogram ... Well, and most importantly, it makes sense to put large-caliber weapons on a fighter, first of all, in order to strike from outside the firing range of the bomber's defensive installations. But the "Japanese miracle" did not solve this problem either ...
        1. zyablik.olga
          zyablik.olga 14 September 2013 12: 43
          But the sleeve was shorter, nevertheless, the NS-45 did not find much use.
      2. Black Colonel
        Black Colonel 13 September 2013 11: 32
        Yes, I once read about the installation of these guns on the MiG-27. An interesting article on an interesting site. The recoil was, of course, very sensitive to the glider.
    2. allekkss
      allekkss 11 September 2013 09: 52
      The increased charge would not have had time to burn out before the projectile exited the gun barrel, and the projectile would have turned into a rocket. Considering its design and materials used, it is impossible to ensure a uniform outflow of gases from all nozzles of the projectile, so the flight path of such a "rocket" after exiting the gun barrel would be unpredictable.
      1. Genry
        Genry 11 September 2013 12: 23
        Quote: allekkss
        The increased charge would not have time to burn before the shell exited the gun barrel

        Everything was in time, or to take another gunpowder.
        Just power should match the mass of the aircraft. Otherwise, hanging-wagging and even destruction.

        The calculation was, apparently, for an attack strictly from above, it is difficult for a heavy bomber to go left and right.
        1. allekkss
          allekkss 11 September 2013 13: 11
          Until the end of the war, Japanese interceptors could not get serial engines with normally working turbochargers (look at the ceiling and the maximum speed that Japanese aircraft could develop despite seemingly powerful engines), so their ability to intercept high-altitude targets (such as the B-29) was very limited. If the Japanese interceptors could attack enemy aircraft with an excess in height, then 30-mm cannons with a high rate of fire would be enough for them. But in reality, the Japanese were forced to "push" behind the American bombers, and then they needed the largest possible ammunition to disable the plane from one hit, since the second time it was not possible to catch the super fortress. And to pick up a variety of gunpowder that would have a higher burning rate than the existing one, and even mass-produce it in order to fill ammunition, and even in 44, it was not easy for the Japanese, to put it mildly. In addition, if you look not even at the air cannons, but at least at the machine guns, you can see that the combustion process also takes place outside the barrel bore, and here you have to disperse just a 7,62 caliber bullet to a speed of 800 m / s, and not a 40mm projectile. Those. the problem of incomplete combustion of the powder charge in the bore has not yet been resolved.
    3. zyablik.olga
      zyablik.olga 14 September 2013 12: 42
      Then the Japanese fighters would fall apart in the air when firing
  3. Rebus
    Rebus 11 September 2013 09: 30
    It’s more like an automatic grenade launcher, and the shell of a VOG-25 shot (or VOG-25 is similar to this shell ...)
    1. luiswoo
      luiswoo 11 September 2013 13: 43
      Quote: Rebus
      It’s more like an automatic grenade launcher, and a VOG-25 projectile

      Well, rather then 7P39 for AGS-40:

      Although really, this is an automatic grenade launcher, not a gun.
    2. combat192
      combat192 11 September 2013 16: 06
      That's right. I thought so too.
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  6. mirag2
    mirag2 12 September 2013 10: 29
    Anyway, the article is interesting.