Looks great, although I think theres a couple of places where I would have skimped more on the polygon count. The screw above the trigger for instance is a little overkill IMO as that side of the gun is rarely seen, not too many lefties in warfare these days.
The end of the barrel is a little OTT as well, really I think to get the most from the model you should make a low poly version with a normal map based on this version. So the screw, the barrel detail, the grip and side extrusions and recesses - these could be left to the normal map, saving lots of polygons.
These are not comments about the quality of the model of course, just some thoughts on using it in a game and how it could cost a bit less in performance while still looking good.
