I don't think I've ever seen a gun do that. You probably could reverse the normals on the model in whatever program you are using to export to .dts. I know that's what happened for my gun. It's barrel's normals were flipped and it had a shiny glow to it.
Normals are basically the faces "flipped" the other way. So when a light hits it, lets say from the right side of it, it would be reversed shadowing giving it a glow. Instead of it casting a shade to the left side it would be lit up.
Does that make sense?