This looks very much like a modified SCAR. As for critiques, I think a far as modelling goes, you are great! You wield 3ds max like a master. As far as the design itself goes, I would say for a sci-fi rifle, especially one based in realism as yours is, it's a major mistake not to go with a bullpup design. When you look at the landscape of modern weaponry, I think it's easy to see the way things are going, and that's towards making bullpup the standard design. More and more countires are adopting a bullpup as their main assault rifle, and some new designs that are respected by all are coming out, such as IWI's Tavor. The major issue people had with the Tavor design were a few odd designs for the shell ejection, and "squishy" triggers, both of which have been mostly fixed. I think within the next 20 years we are going to see a massive growth in bullpups being used by armies around the world (and there are already quite a few that do).