How to texture a gun in Blender?

Ok, I made a glock 18 & an mp5k. When I go to texture using the "UV Editor", I still have white outlines on the side of it. Should I only select the sides I want to texture using that image, and zoom in to correctly match it on perfectly? But what about the top of the gun, and all that? Can I just find a different image of the tops of a gun and when I go to use "Project View", do I resize it on the UV Image Editor to fit the new image of the top of the gun?

Thanks. Your help is appreciated :)