well, i'll have to check it out but i think it's a 30rd mag. On the design, it's not that much different than the original XM29/OICW, they just scooped out some useless areas to make it lighter, streamlined it, and added a much more efficent targeting system, which is the the blue thing at the top. It's a type of IR pointer system, only the soldier looking through the eyepiece or his landwarrior HUD can see the illumintated light dot, kind of like an invisible laser sight. Pretty cool stuff!
P.S. the targeting system can be taken off and replaced by a normal one if wanted, though i don'