Being the proud owner of a Tokyo Marui M733 (AR family, shortbarrelled pre-cursor to the M4 if anyone didn't know) , which the Classic Army gun linked to shares the mechbox/guts design with, there is NO way in hell to turn the thing into a functional weapon without so much work you could actually build a new lower from scratch and come out WAY ahead. You could maybe just maybe make a single shot .22, but it would still take alot of work and be very dangerous.
The idea that you could take a real upper and slap it on and have a functioning AR15 is totally ridiculous. Completely assine crap that this guy is spewing... Tell him yeah it looks real, but it's a toy, moron... And tell him the vast gun industry conspiracy talk is about the looniest crap I've heard all month. If he knew ANYTHING about either guns or airsoft, he'd know what a freakin' idiot he sounds like. Typical antigunner garbage, carry on and on about something they know little to more likely absolutely nothing about...