The 6S8 bullpup anti-materiel rifle, more commonly known as the KVSK, the AVSK or as the Kord sniper rifle, is one of the many types of small arms still flowing into Syria on a regular basis. It sees service alongside the OSV-96 and the Iranian AM.50, both of which now in widespread use in Syria. The 6S8 entered service in limited numbers however, and appears to have been adopted only by a few elite units within Syria's Armed Forces.
The first anti-materiel rifle that reached Syria was the OSV-96, of which a limited number were acquired shortly before the start of Syrian Civil War. The continuing deliveries of Russian OSV-96s and Iranian AM.50s, which started after Iran intervened in the Civil War, ensured a solid presence of anti-materiel rifles in the war-torn country. From that perspective, either increasing the volume of AM.50 deliveries or acquiring more OSV-96s would have made more sense.
Nonetheless, a limited number of 6S8s were shipped to Syria in 2014. A request made by the Army Supply Bureau of the High Command of the Syrian Arab Republic to Russia's Rosoboronexport in early 2013 revealed Syria's interest in one-hundred 12.7mm sniper rifles, but it's likely that this actually refers to the OSV-96 instead.
This theory is strengthened by the fact that several Syrian soldiers recently received lessons on the 6S8 in Russia as part of their training here. Good experience gained with the 6S8s might have been the reason Syria ordered these rifles. One of the Syrian soldiers undergoing training on the 6S8s in Russia can be seen in the image below.
The 6S8 was originally marketed as KSVK, then as ASVK, but was officially adopted as the 6S8 by the Russian Army. To add to all the confusion, it is currently marketed as the 'Kord sniper rifle' by the Degtyarev Plant, which is responsible for the design and production of the anti-materiel rifle. Just like the OSV-96, the 6S8 is chambered in 12.7×108mm, allowing for the penetration of armoured vehicles and public housing.
From Russia with Love, Syria's Vepr-12s
From Russia with Love, Syria's MTs-116Ms
From Russia with Love, Syria's OSV-96s
From Russia with Love, Syria's AK-104s
From Russia with Love, Syria's AK-74Ms