Partway through 1944, the Japanese Imperial Navy began a program to provide their infantry units with better firepower than was afforded by the bolt action Arisaka rifles. The initial experimentation was based on rechambering captured US M1 Garand rifles for the 7.7 Japanese cartridge, but an incompatibility of American en bloc clips with the Japanese cartridge hamstrung the project. In response, the M1 was reverse engineered, and the Yokosuka Naval Arsenal began to manufacture a copy of the rifle which would use a 10-round fixed magazine fed by two standard stripper clips.
This rifle was designated the Type 4 (2604/1944), although it is often referred to today as the Type 5. In total, parts for 200 rifles were manufactured, but only about 125 had been actually assembled into functional guns by the time the war ended.