I am not an expert in texturing, but it seems to as if your metal is not reflecting an environment. (I might be wrong though)
If you want metal to look realistic it needs to reflect something. There are heaps of tutorials out on this topic.
Also the trigger seams to be too rigid, try to shape it a bit more. Not that I ever touched a gun, but I think usually they are shaped sort of ergonomically to suit your finger.