Yes very cool, I'm not seeing anything about them being CO2 though. Maybe I'm blind? You did link to a page with several gun links.
Ideally, I've always wanted the RA-Tech, WE M14 EBR, Open Bolt, Level III, in a CO2 gun. I'd do the silencing mod, and DMR the shit out of it. I'd get a custom decal for the side that says "head shot cannon".
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē