BACK UP YOUR VPK.

-Go to ..\steam\steamapps\common\Counter-Strike Global Offensive\csgo

-Use Notepad++ to edit "pak01_dir.vpk"

-Press Control+H and replace the following words:

-"m4a1_unsil-1" -> "m4a2_unsil-1"

-"v_rif_m4a1" -> "v_rif_m4a2"

- Pick which sights you want and extract the folders to ..\steam\steamapps\common\Counter-Strike Global Offensive\csgo