Ho-103 machine gun

The 12.7mm Type 1 (1941) was a Japanese aircraft machine gun widely used during World War II and also known as the Ho-103.[2] It was based on the American .50-caliber M1921 aircraft Browning machine gun.[1]

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 to 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	900 RPM 400 RPM (synchronized)
Muzzle velocity	770 m/s (2,500 ft/s)
Feed system	Belt 250 rounds
Sights	Iron

The Ho-103 achieved a higher rate of fire by using a smaller, lower velocity Breda (Vickers) cartridge, intermediate in length between the WWII German 13 mm calibre MG 131's 64mm length cartridge, and the long 99mm cartridge of the veteran American M2 Browning .50 calibre gun. Because of this, the gun was frequently loaded with explosive or incendiary ammunition in an attempt to increase its effectiveness.

Types of ammunition used by this gun are:

- Ball, marked with a pink/red seal around the casemouth.

- Two types of Armour Piercing Tracer, marked with a black (red tracer) or green and white (white tracer) seal around the casemouth.

- Ma 102 Fuseless Explosive Incendiary, marked with a dark purple seal around the casemouth.

- Ma 103 Fuzed Explosive Incendiary, marked with a clear (single piece fuze) or white (2-piece fuze) seal around the casemouth.[3]

Some examples of Ho-103 cartridges. From left to right: AP-T (red trace), AP-T (white trace), Ma 103 Explosive Incendiary (two-piece fuze, traces of white seal are still present in the knurles on the projectile), Ma 102 Explosive indendiary.

Variants

The Type 1 was produced in two variants. The Ho-103 was used in fixed installations, while the Ho-104 was used in flexible installations.[1]

Design

The 12.7×81mmSR allowed the Type 1 to fire at a rate of 900 RPM, but the poor suitability of the Browning action to synchronization reduced the rate of fire to 400 RPM in synchronized installations.[1] However, the Japanese source and Allied Intelligence reports[4] did not mention that this machine gun had a propeller synchronization flaw. The source for the Bell P-63 Kingcobra also doesn't mention the propeller synchronization flaw in the browning design.

References

1. Rottman, Page 22.
2. http://www.dragonsoffire.com/aircraft-jarmy.htm
3. Japanese Ammunition 1880-1945 vol. 1, Ken Elks, ISBN 0955186226
4. "Catalog of enemy ordnance material. Report No. 12-b(2), USSBS Index Section 6 - NDL Digital Collections". dl.ndl.go.jp. Retrieved 2020-06-25.

Bibliography

• Rottman, Gordon L. (2010). Browning .50-caliber Machine Guns. Oxford, UK: Osprey Publishing. ISBN 978-1849083300.