Sorry for the .7z file, .zip would make it 280 MB, and even .rar would be 250 MB. Uncompressed size is 895 MB.
Installation:
1. Select the appropriate file by following the filetree.
2. Copy the .DDS texture file.
3. Overwrite the scope texture of whichever mod you have installed.
If you dont have a mod installed, I have no idea where the texture goes, im not much of a modder... somewhere in your gamedata folder I guess.
4. Overwrite the old file, but always keep a backup.
5. ???
6. PROFIT!!!
THQ/S.T.A.L.K.E.R. - Shadow of Chernobyl/gamedata/textures/weapons
Put it here, but I guess, that you will need to rename the scope texture to texture name you want to replace.
or make for every weapon an unique one ;D
Or...