Click on "More from this User" to see 14 more videos of products from SHOT show 2007 by "MilspecMonkey"
A post by "Hawkeye" on the AR15.com board provides detailed disassembly images. In the continuation, see how the barrel and piston assembly is attached and locked in place.
To see links to other products introduced at the 2007 SHOT show (if you've not be following along daily), start at the Friday 1/12 Roundup and follow the links to multiple later posts.
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These images (cropped from those on the AR15.com board), show how the barrel is quickly changed:
The loop handle is used to slide the ring with half screw lugs over the end of the barrel and female end of the receiver, with the loop handle 90 degrees to the barrel and out to the side of the receiver. The loop handle is then turned 90 degrees to lock the barrel in place, and then folded up against the barrel. [This might not be the terminology Magpul uses, but (coupled withthe images) it should give you the general idea.]