Here I have re sculpted and re painted my cannon model where i had to bake an all new set of maps. I didnt want to add too much detail to it because I wanted it to have a new too the battlefield look, like maybe its only been there for a day or 2 and took a few hits. 

 For the normal map i used a combination of Maya baking and Xnormals. Xnormals only did a slightly better job in only small areas but Maya baking took a lot longer time to make because all the re positioning of the envelope i had to do.

 Wire frame

Final look