| Ho-103 machine gun | |
|---|---|
 12.7 mm Ho-103 machine gun on display at the Steven F. Udvar-Hazy Center | |
| Type | Machine gun |
| Place of origin | Empire of Japan |
| Service history | |
| Used by | Imperial Japanese Army |
| Wars | World War II |
| Production history | |
| Produced | 1941-1945 |
| Specifications | |
| Mass | 23 kilograms (50.7 lb) |
| Length | 1,267 mm (49.9 in) |
| Barrel length | 800 mm (31 in) |
| Cartridge | 12.7×81mmSR Breda[1] |
| Action | Recoil operation |
| Rate of fire | 983 RPM[2] 400 RPM (synchronized) |
| Muzzle velocity | 780 m/s (2,600 ft/s) |
| Feed system | Belt 250 rounds |
| Sights | Iron |
The Type 1 machine gun (signifying its year of adoption, 1941) was a Japanese aircraft-mounted heavy machine gun widely used during World War II. It was also known as the Ho-103.[3] The weapon itself was largely based on the American .50-caliber (12.7 mm) M2 Browning heavy machine gun, while the design of its ammunition was initially based on various Italian Breda-SAFAT 12.7 mm rounds. Japanese-designed and produced rounds eventually largely replaced these imported rounds.[1]
The Ho-103 achieved a slightly higher rate of fire (RoF) than the contemporary aircraft-mounted M2 Browning machine gun (AN/M2) by using the smaller, lower velocity semi-rimmed Breda-SAFAT 12.7 mm cartridge. The round was intermediate in length (88 mm) between the WWII German 13 mm calibre MG 131's ‘short’ 64 mm cartridge, and the ‘long’ 99 mm cartridge of the M2 Browning. A high RoF was very desirable among aircraft weaponry; with the ever-increasing speeds of fighters, the window to score hits grew smaller and smaller. Thus, a higher RoF provided a greater density of fire and therefore a greater chance to hit. The compromise of a shorter cartridge to achieve this had drawbacks: Ho-103 rounds had a shorter maximum and effective range, as well as a lower velocity than their M2 Browning counterparts. To compensate for the mild to moderate loss in performance, the gun was frequently loaded with high-explosive incendiary (HEI) rounds. The Italian Breda-SAFAT HEI ammunition was initially copied as the fuzed Ma 103 round, until the fuzeless Ma 102 round was developed, carrying over double the high explosive content of the Ma 103.
