Airsoft Buddy now has in stock the WE 4168 (HK416 replica) gas blowback rifle in tan colour. Costing US$274.00 this is already CO2 compatible but you'll need to purchase the CO2 magazines separately. It comes with a 30-round magazine and a 370-400fps power out of the box on Green Gas and .20g BBs, though this may go lower depending on the climate. Some skirmish sites will not allow CO2 power, so you may just be relegated to target shooting when using CO2 magazines.