Only a couple complaints aside. Depending on what the time period/universe your game is taking place, the holographic sight on the gun may be inappropriate? I say that because it looks a lot like the ones used in Call of Duty and Battlefield. Depending on the setting of the game, that may be a problem. It's still a great design, it even has the adjustment button on it; which is a nice touch.
The gun's body as a whole seems a little on the wide side, and it hides some of the details, like the fore grip and the barrel. The barrel could be elongated, and maybe the fore grip moved up just a bit. And for some reason, I feel the charging handle should be moved back a bit; it looks like it doesn't connect with the magazine feed for some reason.
But other than that, this is fantastic! I can't wait to see how it looks with full details/decals an colored.