Okay, it's not too bad but there are a lot of areas that need fixing.
First off I think looking at this texture there's no way it needs to be a 2048. The material and sharpness of the entire thing is way to blurry or low quality for a 2048. Make it a 1024 please.
-The base metal texture and scratches are not fully utizlizing the spec map.
http://www.dregsld.com/tutorialfiles/tutfiles/SpecularStudy.html
- The wood grains don't blend properly and they don't look like the right type of wood a shotty like that would have. Infact looking at this shotty, it's obviously a mossberg 500, which doesn't have any wood at all. The only wood is a long wooden stock variation.
http://www.flickr.com/search/?q=mossberg+500#page=0
-The barrel is the same type of metal as the rest of the gun. The foregrip was either plastic or metal.
-Texture looks cloudy/grainy. Looks like all you did was add a grain then use gaussian blur. The metal just seems to basic, think of dents and scratches, greasy hands or oil stains. Take a look at this one: It's a mossberg 590 but they should have similar materials.
- Final thing, Please don't render on black backgrounds, it makes it hard to even see a silhouette at all. At least a dark/mid grey.
