First revealed today at an arms expedition in Moscow, the ADS by the Tula Instrument Design Bureau is the world’s first amphibious assault rifle.
When on land, it fires 5.45х39 mm bullets – the current standard round for Russian assault rifles, but underwater this gun utilizes a slightly shorter bullet, whose range is constrained by the depth of diver when firing.
The underwater rounds, known as the 5.45 x 39 PSP, do feature longer slugs designed to move through water rather than air, but are packed into the standardized casing.
This allows special forces to simply swap out magazines when moving from one environment to another and eliminates the need to carry a second rifle.
The ADS has an effective underwater range of 25 meters and is about as as the AK-74 it is meant to replace.
Official Source: http://gizmodo.com/this-russian-rifle-fires-800-rounds-per-minute-underwa-1451570802