User blog comment:Cod1/U.S. Marines with AK-47s/@comment-1790643-20100410072713

@Cod addict. As I said, I've not seen anything about a belt-fed SCAR, so I've probably misunderstood Griever. As for calibre changes, I've read (obviously no first hand knowledge) it's both parts of the receiver; obviously different magazine housings for the lower receiver, and just the ejector port for the upper receiver, as well as the barrel and bolt.

I hope he means 7.62 NATO too, or it's one of these:

http://www.forumammo.com/cpg/albums/userpics/10062/SiskoAnimated.gif