The mp5_upgrade.zip file you have requested: Shadow of Chernobyl / Mods / Weapons / MP5\\VIPER Upgrade - 1.87mb is not available. Perhaps try browsing all files for the game S.T.A.L.K.E.R. Shadow of Chernobyl and upload any files you want to share or are missing. This is the only information we could locate:
This mod adds a scope to the Viper, a custom crosshair, and changed the sounds for the silencer. It also changes the texture of the gun to make it look better ingame.