If you got no scope or black and pink texture download this.Fixed addon: https://garrysmods.org/download/12185/sniper-kit

This download looks like an addon. You need to extract the downloaded zip and put the addon folder in your Garry's Mod addons folder. You should end up with a directory structure similar to below:

steamapps common garrysmod garrysmod addons Sniper Kit <-- Addon folder! e.g. lua maps materials models etc

steamapps