The 7.7x58 Japanese Arisaka (.31 Jap)

By Chuck Hawks


 


 

The 7.7x58mm was adopted by the Japanese military in 1939. The original intention was to replace the previous (and successful) 6.5mm Arisaka with a more powerful cartridge similar to those used by Britain, Germany, and the USA. In the event, both the new 7.7mm and the older 6.5mm served throughout the Second World War.

A new Model 99 Arisaka bolt action rifle was designed for the 7.7mm cartridge. Like the previous Model 1905 Arisaka rifle on which it was based, the Model 99 was an exceptionally strong military action. To the best of my knowledge, the 7.7x58 cartridge has never been offered in a production sporting rifle.

The 7.7x58 was apparently designed to duplicate the ballistics of the famous .303 British service cartridge. The Japanese military load gave a 175 grain spitzer bullet a MV of 2400 fps at a pressure of about 42,000 psi, which is far below what the action can handle.

Visually, the 7.7mm Japanese is a modern looking rimless cartridge with less body taper than the .303 British, although it uses the same .311-.312" diameter bullets. The case length is 58mm (2.27") and the shoulder angle is 25.5 degrees. The case has a .470" rim diameter.

After the surrender of the Japanese Empire in 1945, 7.7mm Arisaka rifles began appearing in the US as war trophies and military surplus. These were frequently used as "knockabout" hunting rifles, and the cartridge proved more than adequate for North American deer hunting. As a point in fact, the 7.7x58 will do anything that can be done with the .303 British, and more. The Arisaka Model 99 is a stronger action than the Lee-Enfield.

7.7x58 ammunition is factory loaded by Norma of Sweden. A 130 grain bullet has been offered at a muzzle velocity (MV) of 2950 fps with 2510 ft. lbs. of muzzle energy (ME).

More popular is the Norma factory load with a 180 grain bullet at a MV of 2493 fps and ME of 2485 ft. lbs. The trajectory of the latter looks like this (Norma figures): +2.6" at 100 yards, 0 at 200 yards, and -10.5" at 300 yards.

Norma 7.7mm factory loads use American style Boxer primers and are fully reloadable. Norma also offers virgin 7.7x58 brass to handloaders. Hornady, Sierra, and Speer offer suitable hunting bullets for the 7.7x58 of 125, 150, 174, and 180 grains. The Hodgdon, Hornady, and Sierra reloading manuals cover the 7.7x58. As with any .30-.303 cartridge, the 150 grain and 180 grain bullets are the most popular.

According to the second edition of the Sierra Bullets Reloading Manual their 150 grain spitzer bullet can be driven to a MV of 2300 fps with 39.9 grains of IMR 3031 powder, and a MV of 2700 fps with 45.6 grains of IMR 3031. The latter load develops 2428 ft. lbs. of muzzle energy. At 200 yards the figures are 2257 fps and 1697 ft. lbs. The trajectory of that load looks like this (Sierra figures): +2.09" at 100 yards, 0 at 200 yards, -8.91" at 300 yards. This should be a good 250+ yard deer load.

The Sierra 180 grain spitzer bullet can be driven to a MV of 2200 fps with 40.4 grains of IMR 4895 powder, and 2500 fps with 45.0 grains of IMR 4895. The ME at 2500 fps is 2498 ft. lbs. At 200 yards the figures are 2138 fps and 1827 ft. lbs. The Sierra ballistics tables show the following trajectory: +2.49" at 100 yards, 0 at 200 yards, and -10.09" at 300 yards. This is a 250 yard big game load that essentially duplicates the Norma factory load.

The 7.7x58 is a good, but redundant, hunting cartridge. Unfortunately, since no new sporting rifles are being produced, its popularity will continue to decline as time goes on. Nevertheless, anyone who owns an Arisaka rifle in good condition is equipped to hunt most North American, or for that matter African, big game. 


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Copyright 2002 by Chuck Hawks. All rights reserved.



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