When you hide behind a object for cover,you can aim without popping your head out. Move the left anolog stick to the left or to the right (Depending on your shooting area) and you will aim at a target when you do press the R1 to shoot the target.And while your target is a reloading press R1 and target, once done and the target is reloading move the right anolog stick up to targets head to perform a headshot.