Oh, goodness, you would NOT want to model in scratches…yeah, an image texture would be best. Maybe make a grunge map for it? Probably make a grunge map for it in Gimp…export the UVs, download some grungy-looking brushes for Gimp (a simple Google search should give you some good results), paint on some scratches (this part is REALLY an art. Too little, you won’t notice anything…too much, it will look like that little bullet fought a war all by itself! Picture reference is good for that kind of stuff), in Blender, make the black parts of the grunge map correspond to something (maybe a shiny underlayer? Just black? Not really sure…I would go with chrome, though), and you have yourself some scratches! (Sorry if I broke down the process too much, figured you might not have added scratches before)
The key to making a good grunge map is to think about what would REALLY be happening to the object that it would get the scratches…did it get spun around during manufacturing, and scratched by a piece of stray metal? Did it get packed really tightly into a box with 70 other bullets? Tell a story.
If you want to put on a bump map, it wouldn’t be a bad idea, either…just for the scratches, though. Also, I’m not looking at your reference, but should the bullet’s metal be a bit less rough in its reflections? Might be a bit more “metal-y” with sharper reflections…might even want to put on a gentle metal texture on it! If you want to go really crazy, you can put in some anisotropic shading in there.
Sorry for the long list of things…I’m tired, and I’m rambling O.o