Assault rifles will likely be the mainstay of any competent Stalker and the vast majority of NPC's will be equipped with one of many types. Assault Rifles in the S.T.A.L.K.E.R. series can be devided into two groups; NATO and former Warsaw Pact weapons.
Warsaw Pact Rifles
These weapons are most likely the first assault rifles that the player will encouter in any S.T.A.L.K.E.R. game. They were designed with ruggedness, reliability, ease of use, and sheer power in mind (despite the fact that many NATO weapons eclipse these and other areas). Most are of the AK family, all have some resemblance to the AK family.
NATO Rifles
NATO weapons typically offer increased accuracy, better ergonomics and a higher rate of fire. All of the NATO weapons in the S.T.A.L.K.E.R. games are chambered for the 5.56x45mm round, which offers less stopping power and penetration than the bullets used by the Warsaw Pact rifles. But offers slightly better armor piercing abilities with the standard round and dedicated 5.56x45mm AP rounds rival the 9x39mm rounds at significantly lower weight.