How do i make my gun sway like in call of duty 4?
Use an animation.
Or use gradual motion using the MAthf.lerp function to make it slowly sway from side to side.
But an animation is MUCH easier.
"duty 4 " I haven’t played it yet.Can you describe your question in another way?
NOTE TO MYSELF: I should use a comment next time. Not a answer! – OrangeLightning 
make it rotate the same way you make the camera rotate. it is simple. one problem you may find is that it begins to move off of the screen. this is simple to fix just use the Mathf.Clamp() function that is how i did it