When making real world weapons, use real world photographs as guides, check videos if you can, a toy version of the gun your making is an absolute god send. Never just make something up as you go along.
I can guarantee that Sureal Chris had concept photo's before even placing his first vertice, and look at the results.
It's too high poly for a game, but it could easily be cut down - personally I find that making low poly versions of real world weapons is a great way to learn and practice, it's fun to make weapons anyway, but coming out with something useful is just a great way to spend an evening.
Might I suggest having another go, considering the weapon itself and it's components, getting photographs or sketches to copy, and trying to make your low poly game object look just like the real thing.