M4a1 + M203 WIP
It's a very good model for low poly requirements, as in-game using or such. Please, post some wires for us to see about the mesh topology 
As you see, Anonymous mentioned up here about the color of the model, because it makes much easier to see any error or misunderstanding in the mesh (the best color is grey). My tip is to go a little bit further, and use things such as lightmapping/specularmapping for a prettier final art for this model.
If you add turbosmooth to the mesh, you can see if there's any error in the mesh too (such as bad corners or stuff like that)
Pretty WIP btw (:










Have you heard of high poly model or maybe not making a black material that makes it impossible to see any details as well as maybe you know adding some specular and lighting the side you want to show off?