Your spec seems way too dark right now. Metal has a relatively high specular, there's no reason your spec should even be darker than your diffuse when texturing metal. If you want the metal darker you should really darken up the diffuse and then hit it with a bright spec and just keep darkening the diffuse until you hit…
Looking much better. However the cuts and scrapes in the spec are far too harsh on the wood! Assuming the scrapes are a separate layer, wack the opacity down on them to about 50% and try it out. The metal however is looking good, the end of the barrel is looking very nice, that is the real stand out bit for me. Again…