Type 1 47 mm at-gun:
In 1938 the japanese Kwantung Army captured some soviet 45 mm at-guns. The Army Technical Bureau started some intense testing. The gun was found superiour to all own models and as it was based on the already introduced type Ra 37 mm gun (it was in fact an upgunned version of the 3,7 cm Pak Rheinmetall) the decision was made to start the development of a similar weapon with a caliber of 47 mm.
There were two large handicaps slowing down the development:
1. The Army High Command saw no use for such a gun
Therefore the development was seen as "basic research" and not supported properly
2. The main requirement for all infantry support weapons was a weight limit to allow easy transport of the weapon by the crew.
Even the type Ra at-gun reached the limit and so an equilibrium had to be found between weight and effectiveness lowering the ap-abilities of the first test guns noticeably.
With the devastating results of the Nomonhan-Incident in 1939 showing a lack of Antitank defense ability of the infantry the weight limit was dropped and the development of the 47 mm at-gun was fastened . In September 1939 the production and testing of the final construction started.
The gun was in general an enlarged version of the type 94 rapid-fire infantry gun using the same breech type and firing mechanism. Two tires allowed a maximum transport speed of 50 kph. The shield was mounted angled. With a total weight of 750 kg the gun was too heavy for crew transport and the penetration of 50 mm/90° on 500 m was compareable to at-guns of other countries of that time.
Production started in Spring 1941 at the Osaka Army Arsenal which tested all guns and supervised allmost all artillery and at-gun production for the japanese Army.
The guns were used in the regimental at-companies.
During 1942 the few guns produced were found useful against the lightly armoured allied vehicles and light tanks but useless against the Mathilda II. After the US Medium M4 reached the battlefields the guns became almost totally useless.
Additional ammunition research lead to an increased penetration of 45 mm/90° on 700 m but the frontral armour of the Sherman still could only be penetrated below 50 m and the side armour below 250 m.
Some 2300 guns were produced and used until the end.
The gun was also mounted on an enlarged gun mount of the type 98 37 mm tank gun and introduced as type 1 47 mm tank gun. This gun was used with the type 97 medium tank Shinhoto Chi-Ha, type 98 experimental medium tank Chi-Ho, type 1 medium tank Chi-He, type 3 amphibious tank Ka-Chi, and type 5 experimental amphibious tank Ka-To in bow-mount.