Nice job Markus! No doubt it has the ROTJ mount. I'll also try some screen grabs soon and see if any detail from the other side can be seen.
In that FH pic, the long section of barrel looks Fatter (could be optical) than the BullBarrel toward the receiver. Maybe it is a phoney tube extension?
Yes, maybe start the "Weird Bunker Blaster Thread" Another interesting build.