The Idea looked better on Paper
In World War Two Japan had a paratroop corps, Germany provided the technical assistance with equipment implementation in the late 1930’s. One of the methods was the use of parachute-equipped containers housing the firearms, this was dropped separately from the paratrooper. In the combat drop at Sumatra (Japanese) and Crete (Germany), both drop zones had problems of weapons containers landing far from troops, resulting being out gunned.
Especially, the experiences of the airborne attack on Palembang in Sumatra, Dutch East Indies, February 13-15, 1942. In that battle, the airborne troops were equipped with standard rifles that were dropped in separate canisters and ended up landing in swamps some distance from the men, who then had to fight with just pistols, bayonets and grenades.
At the outcome the Japanese obviously thought this wasn’t a good idea, and looked at alternatives methods. One idea is to have the paratroops jump with a compact gun. This resulted in a modified Type 38 Arisaka rifle (similar to a Winchester .308) and a folding-stock version. The first proposed plan was the Type 1. The rifle was basically chopped in half at the chamber and McGyvered a hinge door mechanism onto it, thus producing a folding rifle. These rifle were also fitted with bayonet bars under the barrel.
Archives recorded that several hundred folding rifles were used for trials and performance was not very good. Such as the latch system was not very tight, stocks would wobble around, the threaded stud and wing nut would often catch on things and become damaged.
For the full details on the stock mechanism, see the video below from Youtuber Forgotten Weapons:
Wartime Paratrooper Operations
The records are still unclear whether these folding rifle were actually deployed in real operations. Overall, the Japanese paratroopers did not see widespread deployment during the war. All of their operations were primarily raiding operations to seize airfields or strategically vital assets (like oil refineries).
Source: Ian McCollom Forgotten Weapons Youtube, Wikipedia, Nambu World