little update: I got my Matrix airsoft pulse rifle the other day, and wanted to show some comparison shots with the nerf. The only thing I can see that I could change is the angle of the guard thingy over the front of the barrel. All the other differences are just to make it fit better with the Nerf.
The clip cover is as narrow as I could get it and still fit the clip in, and the little gap at the very back bottom of the shroud is the slot to fit the button for the sliding stock when it's all the way in.
Size-wise, the nerf version is about 15% biger than the real deal one and, of course, mine actually has a working grenade launcher and trigger
All-in-all, I'm REALLY happy with how close these are to each other.