would you mind to show us the shotgun without subsurf?
It has a lot of smoothing issues, obviously, but the beautiful thing about doing Blender for fun with a powerful computer is that I don't have to do stuff to optimize as long as it ends up looking good (i.e. fixing smoothing with redundant vertices and subsurf)
Also, I applied the subsurf on the body of the gun, so obviously I can't take that off.
