Extra Weapon Upgrade Slots is a mod for XCOM 2, created by Meatbites.
Description:
This mod will modify all default weapons to have three upgrade slots and exposes the weapon upgrade variable in 'XComMod_WeaponSlots.ini' for easy customisation.
Installation
Extract the zip file into your SteamApps\common\XCOM 2\XComGame\Mods folder and activate the mod in game’s menu..