Forgive me for asking but aside from not having a push forward design, or not having the feed tubes on the top, and not breaking open to load, how are they alike?
I know you said USAS-12 but you didn't really mean the Korean produced shotgun that looks like a M16 and has a box/drum magazine, did you?
At 13 to 15lbs they are Not at all handy indoors nor easy to pack around. That magazine sticks out like a foot long 2x4 and the drum is worse.
[ETA: After wondering and thinking it's obvious you meant the UTAS, which is an easy mistake to make. No worries.]