I used the Boolean modifier to make a hole in my gun and it looks like a shadery face covering up the hole. It's a bit hard to see and it isn't really a face. The hole i made goes through 3 meshes. 

(You need to click on the pic to see the shady face)
[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/7TjEi.png

Here's the file so you can check it out: [<img src="http://blend-exchange.giantcowfilms.com/embedImage.png?bid=404" />](http://blend-exchange.giantcowfilms.com/b/404/)

Any solution?