APS underwater assault rifle and SPP-1 (Russia)

Has no analogues in the world!!!
APS underwater assault rifle (Russia).

Caliber: 5.6x39 mm MPS
Action: Gas operated, rotating bolt
Overall length: 823 mm (butt retracted), 615 mm (butt collapsed)
Barrel length: n/a
Weight: 2.4 kg less magazine; 3.4 loaded
Rate of fire: 600 rounds per minute (in air)
Magazine capacity: 26 rounds

The APS (Avtomat Podvodnyj Spetsialnyj = Special Underwater Assault rifle) was developed during the early 1970s at TSNIITOCHMASH (Central Institute for Precision Machine building) by the team lead by V. Simonov. APS has been in active service with combat divers of the Soviet and Russian Navy since circa 1975.

The APS is designed for special underwater cartridges, which fire 5.66 mm needle-like projectiles 120 mm long. The projectiles are stabilized using a hydrodynamic cavity, generated by the flat point of the projectile. The cartridges use standard 5.45 x 39 cases, sealed from water. The APS itself is a relatively crude, smoothbore arm, with a gas operated, rotating bolt action, fired from an open bolt. Single safety / selector switch is located at the left side of the receiver and allows for single shots and full automatic fire. The gas system features a patented self-adjusting gas valve, which allows the gun to be fired both underwater and in atmosphere. The simple trigger unit allows for single shots and full automatic fire. The rate of fire under water, as well as the effective range, depends on the actual depth. Sights are crude: a non-adjustable open notch rear and post front. The retractable buttstock is made from steel wire. The most complicated thing in the whole design is the feed system, which includes several parts to avoid double and even triple feed with the extremely long projectiles. Unusually deep (front to back) magazines are made from polymer and hold 26 rounds.

It must be noted that while APS could be fired "above the water", it should be done only in the case of emergency. According to the available sources, the expected service life of the APS when fired "in the air" degrades severely, and the effective range is limited only to several tens of meters. So, the APS is useful only under the water, where it is quite efective.
SPP-1 underwater pistol (Russia)

Type: Double Action Only
Caliber: 4.5x40R
Weight: 950 g empty
Length: 244 mm
Barrel length: 203 mm
Capacity: 4 rounds in separate barrels

The SPP-1 (Spetsialnyj Podvodnyj Pistolet = Special Underwater Pistol) has been developed in late 1960s by the TSNIITOCHMASH organization on request from the Soviet Navy. The SPP-1 was intended for Soviet combat divers ("frogmen"). Later the SPP-1 has been modified to SPP-1M, with several internal upgrades, and is still used by Russian Navy special forces, as well as offered for export through Russian Governments' military sales organization, RosOboronExport.

SPP-1 is a non-automatic, manually operated handgun with four barrels. Barrels are hinged to the frame in the same manner as on break-open shotguns. For reloading, barrel cluster is tipped to expose chambers, and four cartridges are inserted into barrels. To speed up ejection and reloading cycle, cartridges are loaded using flat clips, made from steel. The double-action trigger unit consists of a striker, mounting on a rotating base, so during the each trigger pull the striker is cocked and simultaneously rotated to the next, unfired barrel. The single lever, located at the left side of the frame, controls the safety and reloading. It has three positions, top for "Reloading" (barrel release), middle for "Safe" and bottom for "Fire".

To be effective underwater, SPP-1 uses special proprietary ammunition, with rimmed bottlenecked cases 40mm long, sealed from water. Unusually long bullets are made from mild steel, and are drag-stabilized underwater; on air, bullets are not stabilized at all, so the effective range "above the air" is limited, but the "lethality range" is about 15 to 20 meters. When underwater, lethality range degrades with the increase of the depth: at 5 meters depth, the effective range is about 17 meters; at 20 meters depth, the effective range is only about 11 meters.

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