There is a certain Air Force training film series that has a "US servicemember" running around the woods with an AR in the following configuration for well over an hour (its a bunch of short films):
16" barrel
No bayonet lug
A2 upper
A2 stock
7.62x39 frankenmag prominently inserted into magazine well
Kharn
16" barrel
No bayonet lug
A2 upper
A2 stock
7.62x39 frankenmag prominently inserted into magazine well
Kharn