We had a question posted a few days ago, where someone was having difficulty firing bronze with cork clay. I hadn't tried it yet, so that will be my experiment for this week. If they are dry in time, I'll post the results on Friday, but most likely I won't have any information to share until Wednesday next week.
I did a bit of research though, and it looks like you have to use an open air firing first to successfully burn out the core, and then fire again using the carbon.
More information about the open air firing schedule can be found on Margaret Schindel's bronze clay Squidoo lens
If you are in the area this weekend, I'll be hosting a rare Saturday metal clay playday from 10am to 5pm!