APS Underwater Assault Rifle

The APS was developed during the Cold War arms race to counter the growing threat of NATO combat divers and frogmen. Before the APS, underwater combat was limited to knives and spear guns. The Soviet Union's development of a fully automatic underwater firearm was considered a major tactical innovation. The long steel darts fired by the APS are sometimes described as 'underwater bullets' but function more like miniature harpoons, relying on their mass and velocity rather than fragmentation for terminal effect.

The APS can technically be fired above water with an effective range of approximately 50 meters on land, but accuracy is poor because the smoothbore barrel provides no spin stabilization in air. Firing above water also dramatically accelerates barrel wear, reducing barrel life from approximately 2,000 rounds underwater to just 180 rounds in air. The unique 5.66x39mm MPS cartridge uses a modified 5.45x39mm case with a smokeless pyroxyline propellant charge of 1.4g, and the complete cartridge weighs approximately 27.5-28.0g due to the heavy steel dart. The MPS cartridge is also available in a tracer variant (MPST). The APS has been largely superseded by the ADS (Avtomat Dvukhsrednyj Spetsialnyj), an amphibious rifle that can effectively fire both underwater with dart ammunition and on land with standard 5.45x39mm cartridges by swapping magazines. The effective range figures listed are for underwater use at 5 meters depth; on land, effective range is approximately 50 meters.