ADS dual-medium

For several decades, Soviet and then Russian combat divers and Naval commando units were armed with special weapons for underwater combat, including the SPP-1 pistol and APS underwater assault rifle. The main drawback of these weapons is that their effectiveness (and life expectancy) for use above the water is severely degraded compared to standard 'above water' weapons. Therefore, combat divers and other Spetsnaz units, when engaged in amphibious operations (below the water and above), had to carry on the mission two types of weapons - one for underwater use and another for use when on shore or on board of enemy surface vessels. The first known attempt to produce a single weapon which could be effectively used either below or above the water was the ASM-DT experimental 'dual-medium' or amphibious assault rifle, developed in Tula in around 2000. The main problem with ASM-DT was that it still had to use extremely long, specially designed underwater ammunition when submerged, which necessitated overly long receiver, complicated magazine well of adjustable size and two types of magazines. This was found unsuitable for combat use, and further development commenced at the famous arms development facility KBP (Instrument Design Bureau) in Tula. By 2005, design team at KBP has successfully developed effective underwater ammunition which retains the compact size of the standard issue 5.45x39 7N6 ball (as well as 7N10 and 7N22 AP) rounds, and thus can be loaded and fired from standard AK-74-type box magazines, and, more importantly, fired from the same chambers and barrels that would accept the 'above-water' 7N6 ammunition.

ADS dual-medium / amphibious / underwater assault rifle, current model, which can be used in same configuration either above or below the water, with only change being ammunition type (in similar magazines)

This new cartridge is known as 5.45x39 PSP, and is externally similar to standard 5.45x39 ammunition except that it has a different bullet shape. Internally it differs in having a long bullets, which has specially calculated shape and protrudes back into the cartridge case all the way to the bottom, with overall bullet length being about 53mm (2.1 inch), compared to overall cartridge length of 57mm. There are two types of PSP ammunition, the 5.45 PSP (combat ammunition) with hardened steel projectile weighting 16 gram (muzzle velocity on air about 330 m/s) and 5.45 PSP-U (practice / training ammunition) with bronze projectile weighting 8 gram (muzzle velocity on air about 430 m/s). Effective range with PSP ammunition varies from 25 meters at 5 meters depth to 18 meters at 20 meters depth; effective range of the PSP-U training ammunition when below teh water is about 2 times shorter.

ADS dual-medium / amphibious / underwater assault rifle configured for above-water "Spetsnaz"  use; grenade launcher barrel is removed, and a silencer and night sight are installed for special operations

Having settled on new ammunition, designer at KBP commenced work on the new weapon, well suitable for both surface and underwater combat. This new rifle was designated as ADS (АДС - Автомат Двухсредный Специальный - Avtomat Dual-medium, Special). They used the A-91M bullpup assault rifle as a starting point, retaining its bullpup layout, gas operated action with rotary bolt locking and forward ejection through the short tube running above and to the right of the barrel. Some parts of the weapon were necessarily redesigned and materials revised to work reliably when submerged in water, gas system was modified with addition of the environment selector ("air / water"). Integral 40mm grenade launcher (which fires VOG-25 type 'caseless' grenades using additional front trigger inside the trigger guard) is fitted with removable barrel which can be removed when it is not needed by the mission profile. Muzzle of the barrel is threaded to accept muzzle brake / compensator, tactical silencer or blank-firing adapter. Rifle is fitted with adjustable iron sights, and an integral carrying handle is provided with Picatinny type rail on the top to accept various day and night optical sights. The ADS can fire any standard issue 5.45x39 ammunition (ball, tracer, AP) when above the water, with accuracy and effectiveness similar, if not better than of AK-74 / AK-74M general issue assault rifle. When submerged and loaded with 5.45 PSP ammunition, ADS outperforms APS underwater assault rifle in terms of accuracy and ease of handling.

Diagram from original Russian patent, issued in 2006, for the design of the 5.45x39 PSP underwater cartridge and bullet, which protrudes down the cartridge case all the way to its base.

Early prototype of the ADS dual-medium / amphibious assault rifle configured for above-water fire, with standard AK-74 magazine loaded with 5.45x39 ammunition

Early prototype of the ADS dual-medium / amphibious assault rifle configured for under-water fire, loaded with special magazine with underwater ammunition with long, needle-like bullets; it was based on the earlier ASM-DT experimental dual-medium / amphibious assault rifle

Caliber: 5.45x39mm 7N6 / 7N10 / 7N22 for above-water fire and 5.45x39 PSP or PSP-U for under-water fire
Action: Gas operated, rotating bolt
Overall length: 660 mm
Barrel length: 415 mm
Weight: 4.6 kg (with integral 40mm grenade launcher)
Rate of fire: 600-800 rounds per minute
Magazine capacity: 30 rounds