Materials are too clean. Add some dirt and/or wear and tear.
I think your main problem at the moment is the gun itself. It’s very blocky. Even if it’s a futuristic design, it should still feel like something that could actually exist. The hand grip, for example, looks way too sharp, and would be very uncomfortable to hold.
Also, as mentioned, adding some wear and tear, scratches etc…would really add to the overall realism of the model.
The lighting looks really nice, though the scene itself is a little random. I can’t really work out what the story is.
Thanks for the advice 
Try to add some rough metallic bump texture and zoom out camera
Welcome 
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i overexposed it to show that the grip is somkinf of weird… (it has no transition?? ) also overpainted some “bevels”… maybe with different ammount… i’m with @Magnavis … think about where the forefingers and thumb would rest… function before looks… just have one or too looks how to hold real firearms… or your hairdryer 
Great idea thanks
I think you’ve been given a lot of great advice so far - mainly about the textures. I would like to add that the gun grip should have some bump/displacement or even geometry to make that stippling effect. But it’s a really cool design. Very futuristic.
You need to add a lighting source – probably of a gently-contrasting color – to properly illuminate the grip of the gun and the underside of the barrel. The area around the trigger and the area of the body slightly above it is, to my eye, “opaque black.”
It is useful to use the Histogram tool to check the relative level of “white vs. black” (in various colors) throughout the picture. What you’d like to have is a “bell curve” shape. In particular, you don’t want to see “spikes” at either end, since these are “opaque black” or “blown-out white.”
(For an “old-fashioned photography” discussion of this idea, Google “Ansel Adams” and “Zone System.” Even though he worked in a very different medium and technology, the ideas are still relevant.)