I need help finding an RPG system to run a S.T.A.L.K.E.R. campaign.

I want something simple that captures the vibe of a tactical yet fun shootout. I plan to run a short campaign where the players are mercenaries hired to handle a problem in the Zone. Survival mechanics and artifacts aren't the priority; I want something that delivers a solid "gunplay" feel. Listen to the track "Adrenaline" from COD: Black Ops II—that’s the kind of vibe I’m aiming for. I considered using Strain; it’s designed for survival horror, but it’s very straightforward and gives the GM a fair amount of freedom when creating enemies, the stress mechanic this RPG has works well for the physical, mental, and psychic pressures of the Zone. Any suggestions?