This guide will tell you how to Unlock Blue Dot Sight in Modern Warfare 2 on ALL WEAPONS.
The first thing you will need to do is go to the home screen of your game and then click on Weapons from the top of your screen. After that, go to load-outs and choose your loadout weapon which is Expedite 12 (shotgun).
At level 7 of this shotgun, then you will unlock the Cronin mini pro. If you have unlocked this, then you can use this with any weapon.
