TSG's picture shows the stock hanging out the end of the bag. I assume an AR15 with a collapsible stock would fit completely inside the bag?
Those looking for something similar and gotta have it now, I picked up a Fieldline Cobra 43" case at WM for $39.97.
My Tavor (16.5") just fits in the side pocket. I can carry one of my other goodies in the other, main rifle pocket.
http://www.walmart.com/ip/Fieldline-Tactical-43-Cobra-Gun-Case-Black/26357372
The pic below doesn't show them, but there are a few more pockets on the front. The pic on the WM site shows them.