7.7×58mm Arisaka

The 7.7×58mm Arisaka cartridge, Type 99 rimless 7.7 mm or 7.7mm Japanese was a rifle cartridge which was used in the Imperial Japanese Army's Arisaka Type 99 rifle and machine guns, and was the standard light cartridge for the Imperial Japanese Army Air Service, such as the Type 89. The Imperial Japanese Navy (and Imperial Japanese Navy Air Service) never shared weapons or ammunition with the army, instead adopting the 7.7x56mmR, a direct copy of the .303 British round. The cartridge was designed to replace the aging 6.5×50mm Arisaka after seeing the effectiveness of the MG 34 GPMG in action (firing 8×57mm IS full power military rifle ammunition) in China during 1937.[2] Due to a lack of materials, the plan to phase out the 6.5 mm Arisaka cartridge by the end of the war was not completed.

Type 99 7.7 mm rimless
7.7×58mm Arisaka
Type	Rifle
Place of origin	Japan
Production history
Produced	1939–1945
Variants	Type 92 semi-rimmed 7.7 mm
Specifications
Bullet diameter	7.92 mm (0.312 in)
Neck diameter	8.58 mm (0.338 in)
Shoulder diameter	11.04 mm (0.435 in)
Base diameter	12.06 mm (0.475 in)
Rim diameter	12.09 mm (0.476 in)
Rim thickness	1.0 mm (0.039 in)
Case length	57.46 mm (2.262 in)
Overall length	79.6 mm (3.13 in)
Primer type	Large rifle
Ballistic performance
Bullet mass/type Velocity Energy 175 gr (11 g) (Ball) 2,440 ft/s (740 m/s) 2,313 ft⋅lbf (3,136 J)

Type 92 semi-rimmed 7.7 mm
Various Type 92 rounds
Type	Machine gun round
Place of origin	Japan
Service history
Used by	Japan
Wars	Second World War
Production history
Produced	1932-1945
Variants	Type 99 rimless 7.7 mm (Arisaka), Navy type 7.7 mm
Specifications
Bullet diameter	.312 in (7.9 mm)
Neck diameter	.336 in (8.5 mm)
Shoulder diameter	.435 in (11.0 mm)
Base diameter	.473 in (12.0 mm)
Rim diameter	.498 in (12.6 mm)
Case length	2.27 in (58 mm)
Overall length	3.14 in (80 mm)
Ballistic performance
Bullet mass/type Velocity Energy 202 gr (13 g) (Ball) 2,200 ft/s (670 m/s) 2,350 ft⋅lbf (3,190 J)
Source(s): [1]

Design

While the round chambered by the Arisaka rifle used a rimless case, rimmed and semi-rimmed variants were produced for use in some Japanese machine guns. This machine gun ammunition is more powerful, and the altered rim is meant to prevent it from being chambered in a rifle.

Japanese ammunition

All Japanese military ammunition used gilding metal jackets for the bullets of ball and Pentaerythritol tetranitrate (PETN)-filled flat-tipped explosive incendiary rounds. Tracer and phosphorus incendiary rounds had cupro-nickel jackets. Armour-piercing ammunition had a brass bullet with a steel core. The bullet type was signified by a colored band over the case mouth.

Bullet	Jacket	Marking Code	Description
Ball	gilding-metal	Pink or Salmon ring	jacketed lead-core bullet
Armor-Piercing	-	Black ring	brass bullet with a steel core
Tracer	cupro-nickel	Green ring	pyrotechnic core in a lead bullet
Incendiary	cupro-nickel	Magenta ring	white phosphorus core in a lead envelope
High Explosive	gilding-metal	Purple ring	PETN core in a flat-tipped lead envelope

Late war ammunition can still be encountered.

Modern Loadings

The 7.7×58mm Arisaka, as a sporting cartridge, is suitable for most big game with proper bullet selection.

The 7.7 mm Arisaka uses the same .311–.312" bullets as the .303 British,[3] and the standard military load delivered the same muzzle energy as the .303 British. Factory loaded ammunition and brass cases are available from Norma, Graf's, and Hornady, Sierra and Speer also produce usable bullets. Reloadable cartridge cases are produced by reforming .30-06 brass, or fire forming 8x57mm IS cases. Case heads derived from the .30-06 are slightly undersized and bulge slightly just ahead of the web on firing, while the 8×57mm IS derived cases are slightly short. Normal cases of the correct dimensions also bulge slightly, however, as most Japanese rifles of this era had slightly oversized chambers, intended to allow the bolt to be closed on a round even in a very dirty chamber.

7.7×58mm Type 92

The Type 92 (semi-rimmed) 7.7 mm (7.7×58mm SR) was a machine gun cartridge and was primarily used with the Type 92 heavy machine gun and the earlier Type 89 flexible and fixed air-cooled machine guns used on Japanese Army planes.

Bullet	Jacket	Marking Code	Description
Ball	gilding-metal	Pink or Salmon ring	jacketed lead-core bullet
Armor-Piercing	-	Black ring	brass bullet with a steel core
Tracer	cupro-nickel	Green ring	pyrotechnic core in a lead bullet
Incendiary	cupro-nickel	Magenta ring	white phosphorus core over a lead slug
High Explosive	gilding-metal	Purple ring	PETN core in a flat-tipped lead envelope

Gallery

• 
  A cutaway of the round

See also

• List of rifle cartridges
• 7 mm caliber—Other 7mm cartridges
• Table of handgun and rifle cartridges

References

1. Johnson, Melvin M., Jr. (1944). Rifles and Machine Guns. New York: William Morrow & Company. p. 384.
2. Honeycutt and Anthony P. 84
3. http://www.chuckhawks.com/7-7mmArisaka.htm

• TM 9-1985-4, Japanese Explosive Ordnance
• "The 7.7×58 Japanese Arisaka (7.7 mm Jap)" by Chuck Hawks
• "The 7.7 Arisaka" by Bob Forker for Guns & Ammo
• Japanese Ammunition 1880–1945 Part 1; Rifle, pistol and machine-gun ammunition up to 20mm by Ken Elks (2007)
• Modern Reloading Second Edition by Richard Lee (2003), page 487
• Honeycutt Jr., Fred L. and Anthony, F. Patt. Military Rifles of Japan. Fifth edition, 2006. Julin Books, U.S.A. ISBN 0-9623208-7-0.