I change after 4 tubes (40 shots) on my Mini-comp, I could shoot more, but the couple times I've tried I've never mad it very far past 40. Chrono'd with first shot around the 285 mark.
Edit: I know what idkfa is talking about. Phantoms are pure performance, completely modular and well priced. A Carter is generally a single setup (VSC or BBA), and doesn't have the versatility that way. What it does have over the Phantom (in my eyes) is that feeling of luxury