So, nobody recommends seating the cores before heating? Reason I ask is that this thread inspired me to muck around with bonding this weekend and Sunday afternoon finds me failed in two big ways - didn't get much bonding except a little at the very base and lots of porosity when I tore open the finished slugs. This was using a SOWW core that's loose, regular zinc chloride paste flux on a Q-tip, and melting them standing in the LEE pot I also use to anneal the jackets. The jackets are drawn .308 cases that have been wet tumbled.
I'm going to try a little tin in my cores and be much more anal about cleaning the insides of the jackets but I'm still concerned about porosity.