The folks at Madbull Airsoft have designed a nifty Barrett M82 airsoft gun that feeds and ejects Co2 cartridges after each shot. Watch the video below:
Large amounts of Co2 allow the heavy M82-sized bolt to cycle, making the gun more realistic in function and also providing a degree of recoil. The downside is that Co2 cartridges are not cheap at about $0.50 – $0.60 each.