The Zastaba Kulbena CZN-M22 was the issue assault rifle for Section 9 in the hit anime film Ghost in the Shell (1995) directed by Mamoru Oshii. It is a purely fictional weapon designed by its original author Masamune Shirow but obviously lifts elements from existing firearms like the French FAMAS and Belgian FNP90. It is deceptively large, but turned out to be so small that none of the full-sized airsoft AEG gearboxes could fit without significantly altering the original dimensions. So instead I used a Well MP7 AEP gearbox firing plastic 6mm, .20g bbs at approximately 280fps at a rate of 18-20rps with an 8.4V battery. I made this replica back in 2008 and is constructed mostly out of PVC plastic (blue) and plasticated wood for the grips. It weighs 2.5kg empty, exactly the same as what it's alleged to have weighed.
Video montage of construction here:[link]