Seeing the tremendous power displayed by the large-caliber 203 37-mm guns when attacking American-made four-engine heavy bombers, the Japanese Army Aviation believed that it had found the correct direction of development of "local fighter guns".
On the other hand, the Japanese Army Aviation upgraded its guns again and was also forced out by the B-29 Super Flying Fortress, although the defensive firepower of the B-29 is far inferior to the fierce B-17 like a porcupine, but its terrible flight altitude made the Japanese interceptors at that time can only look up to the sky and sigh, before the advent of the new high-altitude fighters, the Japanese interceptor pilots can only use the dangerous action of jumping to fight for a short shooting window, general** The time is only a few seconds, and the rate of fire is of little significance at this time, and the attack power of the aircraft gun has become the most critical factor in determining whether the attack is effective.
Fortunately, the Japanese Army Aviation has some ready-made large-caliber guns ready for use. As early as the end of Showa 16, 1941, the Japanese Army Airlines secretly ordered giant aircraft guns of more than 40 mm from various domestic aircraft gun manufacturers. There are two theories about the purpose of the research and development of this batch of aircraft guns, but it can be basically determined that it is the result of the Army's aviation being nervous about the enemy's super-heavy explosion. The 40 mm 301 guns, the 57 mm 401 402 guns, and the 75 mm 501 Super guns were put into service.
It's really not a spit out to say that the Japanese giant guns are weird, for example, the 301 40mm gun is actually more similar to a caseless shell. Speaking of caseless shells, it seems to be a very sophisticated thing, more than ten years ago, the American XM297 Crusader artillery hyped the concept of liquid propellants, and everyone was confused.
In fact, as early as the Civil War, there were already people who developed fragile shells, and after the cannon was fired, the shell fragments were also blown out of the barrel. However, the caseless bullet made by the Japanese is more similar to a spray bomb - it is attached to a propellant combustion chamber in the lower part of the bomb body, which can also be regarded as a solid rocket engine thruster, and the propellant ignites when fired, and a large amount of gas is ejected from the small hole in the lower part of the bomb body, pushing the shell out of the chamber.
The 40-mm 301 cannon uses a spray-in shell, and the color pictures on the left and right are the structure of the **-type grenade, which is almost exactly the same as the spray shell of the aerial gun.
But who may have said to my friends who have seen my previous ** said that in 1941 the Japanese had not yet obtained the German rocket ** data, where did they learn this design?In terms of structure, this design should have evolved from the Japanese grenade canister special grenade, the ** type heavy grenade canister, both in shape and structure, and the 40 mm 301 aircraft gun shell are quite similar, it is estimated that the Army Aviation Technology Research Institute referred to the design of the ** type grenade when developing ammunition.
The biggest advantage of using the jet-in-the-bullet design is that the mass of the whole gun is greatly reduced, but due to the small caliber, the advantage of small recoil of the rocket artillery is not outstanding, after calculation, the recoil of the 301 40 mm gun is about 800kg, which is about 100kg larger than the 203 of the short-barreled automatic type.
The 301 40-mm gun had an 8-round magazine.
However, in terms of the mass of the whole gun, the mass of the 203 reached 90kg, while the 301 40mm gun was only 40kg. Considering that the original 1941 203 did not yet have burst capabilities, the barrel length was longer than that of the later automatic type, and the overall gun mass was greater, the 301 40mm aerial gun should have been the best lightweight large-caliber automatic gun in the hands of the Japanese Army Aviation before 43.
The 301 40mm cannon weighs only 40kg, and the structure is lightweight.
This lightweight naturally comes at a cost, first of all, the 301 gun has a small number of reloads, it uses 8 rounds of magazines to feed ammunition, and the firepower lacks continuity, but theoretically it can be manually reloaded (590g per round, and the full weight of 8 rounds of magazines is about 5kg). Secondly, its automatic parts and mechanisms are too simplified, the strength is very limited, generally after the launch of 100 rounds must be disassembled and repaired, otherwise it is very easy to get stuck, and the data of this 100 rounds is obtained from the ground experiment, the internal vibration intensity of the air body is much greater than the ground experiment, so the Japanese ground crew almost needs to be overhauled immediately after each operation to ensure that the next 301 40 mm guns will not strike in the next lift-off operation (more bitter than the logistics of the German army).
In addition, the muzzle velocity of the ammunition is very low due to the use of jet shells, and the Japanese Army Aviation believes that the muzzle velocity of the 301 cannon at 220m s is also suitable for hitting large enemy bombers. Due to the low muzzle velocity of the ammunition and the slow self-rotation speed, the 301 40 mm cannon has a very short range and an extremely curved trajectory, which is difficult for the average pilot to adapt to.
But like many bizarre Japanese designs, the curved trajectory of the 301 40mm gun became a deadly edge in the hands of some monster pilots. It is said that Ryotaro Uebo, the famous ace of the Japanese Army Aviation, was good at using the curved trajectory of the 301 40mm cannon to attack the B-29 in an incredible flight position (just like the recent war thunder updated with a large wave of howitzers, the curved high-explosive projectile trajectory can hit many places where the high muzzle velocity tank gun can't hit).
Ryotaro Uebo shot down a total of 12 B-29s, and his best aircraft was the Ki-44-II B-2 fighter, Zhong Kui, which was once written about by Japanese pilots who thought it was too fragile to look like a man. However, the light body of this girl fighter is very suitable for rapid jump attacks, and the light body of the 301 40mm aircraft gun is also easy to stuff into the wings of the Ki-44, and a group of old birds of the Japanese Army Aviation such as Uebo Ryotaro used the Ki-44's rapid jump ability with the curved trajectory of the 301 to smash the 40mm spray bullet into the U.S. B-29 like a high-throw shot, and this strange attack method has achieved a lot of results.
Equipped with two 301 40mm guns as wing guns, the Ki-44-II B-2 single-action fighter "Zhong Kui" B modification.
In addition to equipping the Ki-44, the 301 40mm cannon was also equipped with the Ki-45 Dragon Slayer, including the Type II Fuzhan Type E equipped with radar (radio equipment), but because the native air defense team of the Japanese Army Aviation was not equipped with the Ki-44-II B on a large scale until 1944, there were few elite pilots left in the Japanese Army Aviation at this time, and the level of equipment and supply was greatly reduced, and the performance of the B-29 was much ahead of the Ki-44, so in general the 301 40 The millimeter cannon was lackluster in service with the Japanese Army Aviation and was far inferior to the combination of the German MK103 cannon and the ME262 next door.
The 301 40mm cannon was also armed with the Ki-45 Dragon Slayer.
But the Japanese Army was still not satisfied, and they were already eyeing a larger caliber - 57 mm.
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