No, no. I don't like the idea of shells, I was just stating that the TSD's use magazines and still shoot multiple rounds at a time.
I'm saying that you could use a similar, and I use the term similar loosely, system to the one found in the TSD's that replaces the spring power with gas power. It would take much more gas than the usual GBB, but I think someone could get a system similar, again used loosely, to that to work.