The best advice I could give would be to check out reference pics of actual guns, to see how the light reflects off them, depending on finishes. That's what I did here:
It's about fluff, angst, drama, comedy, gaming. Come play in our world.
It's not too hard. Look at the shinier pieces of her outfit and work like that. Just make sure the shadows on the surfaces of the gun agree with the shadows in your picture, and put some highlights on the parts opposite the shadows.
Though I hardly ever draw guns up close, so I'm no expert. Just treat it as any other shiny object.
Hey geetkblather, if that guy fires that gun he's probably gonna loose a thumb.
I the case of silver guns, your best be would be high contrast light and shadows. the shading your using now suggests that as light hits the gun, it becomes dispersed rather than reflected, which is really charicteristic of more soft or textured surfaces like fabric. In this case you want nice bright highlights to follow the edges of the gun which are exposed to light.