Now this is cool. I found this link while reading about the latest developments in back pack systems to feed machine guns. I will not comment on if this is a good move or not, because I have yet to hear any serious testing with this kit, but it is an interesting concept.
As to the film below, I do not know much about this particular AR 10 model. But what a cool concept to be able to switch from belt-fed 7.62 caliber machine gun mode to magazine fed rifle, and have that capability within the compact size of an AR 10? Although the downside would be the barrel and not being able to switch it out, or the amount of heat it would be exposed too. It would be fun to see a modern gun manufacturer pick up where Stoner left off with this design. Modern materials might make something like this viable. Check it out. –Matt