SVDK is a Russian sniper rifle

Sniper rifle

In military and law enforcement terminology, a sniper rifle is a precision-rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military...

 from the Dragunov sniper rifles family chambered for the 9.3x64mm Brenneke

9.3x64mm Brenneke

The 9.3x64mm Brenneke is a rimless bottlenecked centerfire cartridge developed for big game hunting. As is customary in European cartridges the 9.3 denotes the 9.3 mm bullet diameter and the 64 denotes the 64 mm case length. Using the bullet diameter is unusual in German cartridge...

 cartridge.
The Dragunov SVDK large caliber sniper rifle (any rifle caliber above 9 mm is considered a large caliber in Russia) is a somewhat controversial weapon, recently adopted by Russian army. It was developed through "Vzlomshik" (Breaker) research and development program, along with 7.62 mm SV-98 sniper and 12.7 mm ASVK anti-materiel rifles. The purpose of SVDK is to deal with targets which are too hard for standard 7.62x54R sniper rifles like SV-98

Sv-98

The SV-98 is a Russian bolt action sniper rifle designed by Vladimir Stronskiy.-Design details:The SV-98 sniper rifle is based on the Record full bore sport shooting rifle series also made by Izhmash....

 or SVD, such as assault troops in heavy body armor or enemy snipers behind cover. There also were rumors that SVDK will serve as a long-range anti-personnel weapon.

The effective range of SVDK is cited as 'about 600 meters'.