Japanese 40mm Ho 301 aircraft gun caseless

[genkideskan]

These gun was inspired by the army mortar Type 89. The 50mm shell has two compartments, a front compartment holding the explosive charge and a back compartment with the propellant. These mortar was a rifled muzzle loader and the shell used a plain copper driving band. It was fired by a striker pin hitting a central primer cap - the propellant blow out the driving bands into the rifling and shoot out the shell.


Cutaway by D.Harms



Very similar to that is the 40mm ammo. The gun is a blowback system using a 10 rd. box magazine and fire the 40 x 129 shells (caseless) with a conventional copper driving band. The gun fires 425 rds./ min with a velocity of 245 m/ sec. With a weight of 40 Kg and a length of 1, 39 meter it was a compact gun.
The shell used a somewhat different alluminium fuze better suited to aircraft use, a 40mm caliber and a somewhat bigger propellant compartment.








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[timshatz]

Pretty impressive.

Any ideas on how they performed? Stopage problems? Accuracy? Muzzle Veolocity?

How would they compare to something like the Soviet 37MM weapon?

 

[Fokker D21]

They didn't perform very well because of the low muzzle velocity (246 m/s).

Nice pics genkideskan.8)

 

[Fokker D21]

A comparison between Ho-301 and NS 37:

..............................Ho-301............NS 37
Muzzle velocity..........246 m/s...........900 m/s
Projectile weight........585 grams........732 grams
HEI percentage..........9,7%...............6,6%
Fire rate per minute....450.................250
Gun weight................132 kg............170 kg

Gun power.................1249...............1363
Gun efficiency.............9,46...............8,02

 

[Micdrow]

Interesting stuff there guys, thanks!!!

 

[timshatz]

Thanks Fokker, appreciate the info. Was curious about it. Seems lot of Japanese weapons had problems with muzzle velocity, keep getting numbers on the low end.

Is the NS-37 the Soviet weapon? Have read they made the best air cannons in the WW2 period.

 

[Fokker D21]

The NS 37 is the Soviet weapon.

Actually most Japanese Army and Navy weapons were compatitive with those of other nations in terms of muzzle velocity. Japanese Navy Type 99-2 (20mm) has 750 m/s and Japanese Army Ho-5 (20mm) has 700-730 m/s. Compare this to German MG 151/20 with 720-800 m/s and British Hispano II with 860 m/s. Only the Hispano stands out.

It's just the caseless Ho-301 that has such an extreme low muzzle velocity.

From the point of efficiency (gun power versus gun weight) the Soviet aircraft guns were often the best (Berezin UB series and B20). Most Soviet fighters however only carried limited amounts of guns which often had to be synchronized, so their fighters only had average firepower.

 

[genkideskan]

The Ho 301 was used in great numbers only in the Ki 44 Tojo. The gun was planned for some experimental army fighters.


Ho 301 in wing mount Ki 44 Tojo

Close up of an Ho 301 captured at Clark field.

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[Steven Que]

A big gun. Right?

 

[KrazyKraut]

It was a dedicated anti-bomber gun, kind of like a MK-108, only even more extreme. Effective range was supposedly 150 meters and with its high rate of fire I could see it being effective against slow bombers at almost pointblank range. Aiming was probably very demanding, but then, 1 hit would've been enough most of the time.

 

[CharlesBronson]

The muzzle velocity was the same as in a Colt 1911, not very promising really for a A/C gun, but it seems that it take its toll in some B-29s, the terminal ballistic rely entirely in the explosive content.

 

[BlackSheep]

A comparison between Ho-301 and NS 37:

..............................Ho-301............NS 37
Muzzle velocity..........246 m/s...........900 m/s
Projectile weight........585 grams........732 grams
HEI percentage..........9,7%...............6,6%
Fire rate per minute....450.................250
Gun weight................132 kg............170 kg

Gun power.................1249...............1363
Gun efficiency.............9,46...............8,02

Interesting that the HO-301's muzzle velocity is about the same as the ammo used in the Mk19 grenade launcher. Talk about a rainbow trajectory....