Third Person Shooter (TPS) aiming like Uncharted / MaxPayne3

Hello, I would ask you to help create a targeting system in the third person that looks like Uncharted 3 or Max Payne, you can walk and shoot sideways.

I've tried using the IK Unity4, adding a weapon in the player's hand and putting a ik a target to aim up, worked well with guns, but with heavier weapons did not seem realistic, as held and fired with a AK-47 with only one hand, the best would be to combine the IK and animation, but do not know how to do this.