Go to (In OPENIV)
GTAV/mods(if you use mods folder, if not skip)/update/x64/dlcpacks/patchday8ng/dlc.rpf/x64/models/cdimages/weapons.rpf/

drag n' drop.
The pd2 skin are textures that are true to the payday 2 scar-h which includes the tape and stock reskin in bumps and spec maps too.
Especially proud of the drum mag since I had to partialy remodel it and it was my first time modelling something and uv-mapping it.