This guide will tell you how to unlock SLIMLINE PRO Red Dot in Modern Warfare 2.
You have to go to the home screen of your game and then click on weapons from the top of your screen. After that, go to loadouts, choose your loadout weapon, and press X on it. Then you have to go to a gunsmith in the bottom left corner of your screen.
Now you have to go to opt-in, it will show you the weapons that are unlocked in opt-in. It will also show your gun level. Then from the attachments list, you have to select the slimline pro red dot. To unlock it, you have to fulfill the requirements shown under it. If there are no requirements, then you have to wait for future guns.
