Nice gun but 4k sounds excessive. Pretty sure you could do kickass skin with half that resolution. 5.7k tris on the other hand sounds average/slightly low. Could have spent more polies on the details which are right in the players face like the screw and that corrugated thingy. instead of making it completely normal map.
With weapons it's common mistake of artist to spread details evenly so it looks good on portfolio when for actual games (and people judging your portfolio) it's important to focus the detail on the things which are closest to the first person camera (polies aswell as texture density).