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The 6.5×50mmSR Arisaka is a semi-rimmed, full-power rifle cartridge, with a 6.5mm (.264 in) diameter bullet. It was adopted by the Imperial Japanese Army in 1897, in conjunction with the Type 30 Arisaka infantry rifle and carbine.

History[edit | edit source]

The 6.5x50mmSR cartridge was adopted by the Imperial Japanese Army in 1897, alongside the Type 30 Arisaka infantry rifle and carbine, replacing the 8×52mm Murata round and the Type 22 Murata rifle, respectively. In 1902, the Imperial Japanese Navy chambered its Type 35 rifle for the cartridge as well. In 1905, the round also came to be offered in the Type 38 Arisaka infantry rifle and carbine, which rendered the Type 30 obsolete in imperial army service. Type 44 cavalry carbines, first adopted in 1911, were also chambered in 6.5×50mmSR.

The 6.5mm Japanese round was criticized as being underpowered in comparison to American and European military cartridges such as the .30-06 Springfield.303 British7.92×57mm Mauser and 7.62×54mmR. For this reason it was later replaced by the more powerful 7.7×58mm cartridge. As it was, the 6.5mm round with the Type 38 spitzer bullet had a desirable flat trajectory, and effective terminal ballistics with rapid yaw on impact causing severe wounds. Larger caliber military cartridges are also optimal for machine guns to use for long-range firing, and rifles were often only made to chamber them in the interest of logistics. Japan had the 7.7mm cartridge in use only by machine guns for years before developing a rifle for the round.

Design[edit | edit source]

The initial design of the 6.5×50mmSR cartridge had a cupronickel, round-nosed bullet weighing 10.4 grams (160 gr) fired with approximately 2.0 grams (31 gr) of smokeless powder. This was later changed with the adoption of the Type 38 when Japan, in line with the other great powers around the same time, changed to the pointed, or spitzer, bullet in the first decade of the twentieth century.

The Type 38 spitzer round fired a 9.0-gram (139 gr) bullet with a powder charge of 33 grains (2.1 g) for a muzzle velocity of around 770 metres per second (2,500 ft/s). The Type 38 spitzer version of the 6.5×50mm cartridge remained unchanged until after the adoption of the Type 11 light machine gun in 1922. The relatively short barrel (17.5 inches) produced excessive flash with standard ammunition (initially intended for Type 38 rifles with barrel more than a foot longer).

A new loading was introduced for this reason, which had a slightly lower muzzle velocity (under 100fps), but burned much more completely in the Type 11 short barrel and produced much less flash as a result. This new round was called the 6.5×50mm Arisaka genso round, the cartons identified by a circled "G." This special ammunition was also issued to soldiers carrying the Type 96 light machine gun introduced in 1936, and to snipers issued the Type 97 sniper rifle, introduced in 1937. The advantage of the reduced charge ammunition to the sniper was that it aided in his concealment as the reduced charge rounds produced less muzzle flash than standard rounds and thus did not give away the sniper's position.

6.5 mm gallery ammunition: this variant incorporated a paper or wood bullet, and were often used in both civilian and military practice applications.These were either all brass rounds or, more commonly, red varnished wood with a metal base and rim. They can be identified by the staked primers.

Dummy rounds: Similar to Gallery Ammunition, dummy rounds were used in the spigot-type Japanese grenade launchers, often with paper bullets.

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