SKS Type 56 Semi Automatic Rifle – 7.62x39mm. The SKS is a gas-operated, semi-automatic rifle chambered for the Russian 7.62x39mm round. It has a fixed, non-detachable 10-round magazine, wood stock, and a manual safety. The SKS Type 56 is a manufactured version of the SKS. The original Soviet SKS itself proved a reliable and low-maintenance self-loading rifle that required little training in its use and was based internally on the Simonov PTRS anti-tank rifle.