Engineering:Ho-103 machine gun

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Short description: 12.7 mm machine gun aircraft armament
Ho-103 machine gun
12.7mmHo-103.jpg
12.7 mm Ho-103 machine gun on display at the Steven F. Udvar-Hazy Center
TypeMachine gun
Place of originEmpire of Japan
Service history
Used byImperial Japanese Army
WarsWorld War II
Production history
Produced1941-1945
Specifications
Mass23 kilograms (50.7 lb)
Length1,267 mm (49.9 in)
Barrel length800 mm (31 in)
Cartridge12.7×81mmSR Breda[1]
ActionRecoil operation
Rate of fire983 RPM[2]
400 RPM (synchronized)
Muzzle velocity780 m/s (2,600 ft/s)
Feed systemBelt 250 rounds
SightsIron

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 sourced from various Italian Breda-SAFAT 12.7 mm rounds. Japanese-designed and produced rounds would eventually mostly replace 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.

Ammunition

The Ho-103 used a wide variety of ammunition; Most was produced in Japan, but some was imported from Italy (such ammunition was identical to that used in Breda-SAFAT HMGs). Types of ammunition used by the Ho-103 include:[4][5][6]

Some examples of Ho-103 cartridges. From left to right: AP-T (red tracer), AP-T (white tracer), Ma 103 HEI (two-piece fuze, traces of white seal are still present in the knurles on the projectile), Ma 102 HEI.
  • Ball (full metal jacket), marked with a pink or red seal around the casemouth.
  • Armor piercing (AP) of Italian origin, marked with a black tip.
  • Armour piercing tracer (AP-T) with red tracer, marked with a pink tip and green and white seal around the casemouth.
  • AP-T with brighter-burning, longer-lasting red tracer, uncolored tip and black seal around the casemouth.
  • AP-T with white tracer, uncolored tip and green and white seal around the casemouth.
  • Fuzed high-explosive incendiary (HEI) of Italian origin, its body painted blue or red. Contained 0.8 grams (12 gr) of PETN and incendiary composition.
  • Ma 103 fuzed HEI, marked with a white seal around the casemouth. Contained 0.8 grams (12 gr) of RDX and 1.46 grams (22.5 gr) incendiary composition.
  • Ma 102 fuzeless HEI, marked with a dark purple seal around the casemouth. Contained 2 grams (31 gr) of PETN + RDX and 1.46 grams (22.5 gr) incendiary composition.

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 12.7×81mm cartridge allowed the Type 1 to fire at a rate of 900 RPM, but the poor suitability of the Browning's action to synchronization reduced the rate of fire to 400 RPM in synchronized installations.[1] However, the Japanese source and Allied Intelligence reports[7] did not mention that this machine gun had a propeller synchronization flaw.

References

  1. ↑ 1.0 1.1 1.2 1.3 Rottman, Page 22.
  2. ↑ Catalog of enemy ordnance material. Report No. 12-b(2), USSBS Index Section 6
  3. ↑ "JAPANESE ARMY". http://www.dragonsoffire.com/aircraft-jarmy.htm. 
  4. ↑ USGPO (16 Mar 1953). "4". Japanese Explosive Ordinance (Army Ammunition Navy Ammunition). 2 (1 ed.). Washington, D.C, USA: United States Government Printing Office. p. 279. TM 9-1985-5/TO 39B-1A-12. https://drive.google.com/file/d/0B0IDUb3m4SPmRFRxREZTRzhNaTg/view?resourcekey=0-jBjM-8h_MPml_li0UpqE-Q. Retrieved 2021-09-20. "Ball... A. P . T... H. E. I . fuzed... H. E. I . fuzeless... H. E . I . fuzed (Italian)... Tracer... A.P. (Italian)" 
  5. ↑ Chief Inspector of Ammunition (1945). Japanese Ammunition. 24 (2 ed.). Khadki, India: Chief Inspector of Ammunition, Kirkee. pp. 3–4. https://drive.google.com/file/d/0B0IDUb3m4SPmNFd6TExoR2FYLTA/view?resourcekey=0-_Hk7-ewDAp_M02LDwgsmPA. Retrieved 2021-09-09. 
  6. ↑ Japanese Ammunition 1880-1945 vol. 1, Ken Elks, ISBN:0955186226
  7. ↑ "Catalog of enemy ordnance material. Report No. 12-b(2), USSBS Index Section 6 - NDL Digital Collections". https://dl.ndl.go.jp/info:ndljp/pid/4009929/78?itemId=info:ndljp/pid/4009929&contentNo=78&__lang=en. 

Bibliography

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



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