I am a newbie.Please let me know how can i improve it ?
You should also skew the grip for added comfort and realism. Also needs the end of the barrel where the bullets (?) come out and some kind of bolt or moving parts.
I think it could look good already if you now added some engraved text (paint displace/normal texture with stencil texture) and wear and tear via diffuse or normal/spec maps.
Looks funky, I like funky.
The stock positioning seems a little odd, you might need to move it up or add a cutout for the characters thumb?
I suspect the background is just a placeholder, but I want to point out a compositional error. notice how the edge of the barrel lines up with the horizon. I forget the term, but such an accidental alignment skews depth and draws the eye in unintended ways.