are you sure sure, cuz i've never heard of a CO2 powered airsoft gun. only for metal bb's. it wouldn't make much sense either cuz that would be way too much power for such a light and round and big trajectory. it would be way in-accurate. but i'll say one thing for sure, the cartridges are definitely not refillable.
jw if you could lower the days. I know people hate when they get asked that but im willing to bid alot if its a possiblity, and i know you already made it free shipping =)