Type 4 rifleGas-operated, rotating bolt; 7.7×58mm Arisaka from a 10-round internal magazine
If you can’t beat them, join them. A Japanese experimental semi-automatic rifle, the Type 4 was a copy of the M1 Garand but with an integral 10-round magazine and chambered for the Japanese 7.7×58mm Arisaka cartridge.
During the Second World War, Japanese soldiers relied on bolt-action type rifles. However, as the war went on, guns were getting scarce and their main military rival, the United States, had replaced their bolt weapons with semi-automatic rifles which gave them great advantage on the battlefield. This pressured Japan to find a quick way to cope with their military disadvantage. Instead of designing and investing in a new weapon from scratch, they opted to copy the American M1 Garand.
Initially, the Japanese experimented with re-chambering captured American M1 rifles, since the 7.7 Japanese cartridge is dimensionally similar to the .30-06. They found that while the Garand could chamber, fire, and cycle with the 7.7 ammunition, the en-bloc clip system was incompatible with the cartridge and would not feed reliably. Instead the Japanese designers reverse engineered the M1 and discarded the en-bloc clip, replacing it with a fixed internal 10 round magazine charged by two 5 round Arisaka Type 99 stripper clips.
Japan had previously developed semi-automatic service rifles, but none of them had been viewed as successful or of trustworthy quality. The design work for the Type 4 began in 1944. The rifle was meant to be mass-produced in 1945. However, the Japanese defeat in the war in August halted its manufacturing. At the time, only 100 guns were completed out of the 250 in the workshop. Twenty of them were taken by the Allies at the Yokosuka Naval Arsenal on Honshu after the end of the war.