How to get the Roturret trophy

To get the Roturret trophy you have to get to the end of Skyworld. Make sure you have a trophy stand before you get to the area where you fight a lot of cloud creatures. There will be Primids, Boom Primids and Sword Primids. Whenever you are done killing all of the Primids, use Snake to go under the Roturret and use his homing rocket launcher and grenade launcher. Once his health is low, throw the trophy stand at him. It should be easy to get him.