The 4.5 mm SPP-1 Underwater Pistol was made in the USSR for use underwater by Soviet frogmen as an underwater firearm.[2] It was developed in the late 1960s and accepted for use in 1971. Underwater, ordinary-shaped bullets are inaccurate and very short-range. As a result, this pistol fires a round-based 4.5 mm caliber steel dart about 115 mm long (about 4.5 inches), weighing 12.8 g, which has longer range and more penetrating power than speargun spears. The complete cartridge is 145 mm long (about 5.7 inches) and weighs 17.5 g.[6]

The SPP-1 has four barrels, each containing one cartridge. Its ammunition comes as a clip of four cartridges which is inserted into the pistol's breech.[5]

Its barrel is not rifled; the fired projectile is kept in line by hydrodynamic effects. As a result, it is somewhat inaccurate when fired out of water.[1]

Depth reduces range because the higher pressure closes the cavity sooner. Once the projectile is no longer supercavitating, hydrodynamic drag increases greatly, and the projectile becomes unstable.

Lethal range is defined as the range from which it can easily penetrate a padded underwater suit or a 5 mm thick glass faceplate.[4]

A double-action firing mechanism fires one cartridge sequentially for each pull of the trigger. When all four cartridges are spent, the gun can be reloaded above or below water.[2]

The SPP-1M pistol is essentially the same as the SPP-1, with the following differences:[5]

   * It has an extra spring above the sear to improve the trigger pull.
   * Its trigger guard is larger to accommodate diving gloves.

The weapon was designed by Vladimir Simonov, the cartridge by Pyotr Sazonov and Oleg Kravchenko.[1] Simonov also designed the APS amphibious rifle.[7]

It is manufactured by TOZ (Tulsky Oruzheiny Zavod/ Тульский Оружейный Завод) Tula Arms Plant,[3] and exported by Rosoboronexport,[2] the state agency for Russia's export/import of defense-related products.

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