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.

In late 1940, the US military opened a competition for what would become the M1 Carbine - a rifle that needed to use the .30 Carbine cartridge and weigh no more than 5 pounds (2.27kg). No fewer than 9 companies and designers entered the first round of competition in April 1941, including John Garand, Val Browning, Eugene Reising, Auto-Ordnance, and George Hyde. Hyde's entry was one of the best performers, and just a few changes to it were requested.

A second round of trials was held in September 1941, and this is one of the 5 Hyde carbines made for that second test. Unfortunately for Hyde, while he had made the changes requested, he had also managed to make the gun less accurate, less reliable, and more difficult to disassemble than his first version. Winchester would ultimately win the competition, with a rifle designed in an amazing 34 days.

The Type 100 (sometimes called the Type was one of the initial Japanese experiments in paratroop rifles. Manufactured from standard Nagoya Arsenal Type 99 rifles, the Type 100 used a set of interrupted lugs at the chamber to allow the rifle to be broken into two short sections. Only a few hundred of these were manufactured for testing, and ultimately the Type 2 design (with a locking wedge) was adopted instead.

The Hamada was one of very few Japanese military weapons made by a private commercial firm. Designed and introduced in 1940, the basic Type Hamada pistol was a blowback .32ACP handgun similar in style to the Browning model 1910. About 5000 of them were manufactured during WWII, although most of these were sent to China. All the known examples in Western collections are form a fairly narrow serial number range (~2200-300, which probably represent a single batch rerouted to the Pacific islands, where they were occasionally captured by US troops.

In 1943, Hamada was asked to develop a pistol in 8mm Nambu to simplify ammunition logistics, and this would become the Type 2 Hamada.

Just as production of the .32ACP Type Hamada pistols was reaching full scale, Bunji Hamada was asked to redesign his pistol to use the standard 8mm Nambu cartridge. This he did, and after several changes required by the Army (which appear to have had more to do with giving the Army some claim to the design rather than for any practical reasons) it was adopted in 1943.

Production of the .32ACP pistols continued uninterrupted, while a defunct textile factory in Notobe was renovated to become the production plant for the new Type 2 Hamadas in 8mm. Machinery was provided by the Torimatsu factory, and the guns were to be sent to Torimatsu in the white for final finishing operations.

While several thousand were made according to surviving records, the only ones still known in existence today have serial numbers between 2 and 50 and are still in the white. This suggests that aside from a small initial (sample?) batch, all the Type 2 Hamadas were destroyed or lost - possibly by aerial bombing or during transit on the ocean.