I know there are lots of threads out there on mold cleaning, and I have read as many as I can find, but so far, no luck, so maybe someone here can help me. 
Several years ago, I got some zinc contamination in my lead. I had to buy  a new melting pot and mold,  and to this day I cannot get good bullets out of the aluminum mold that was affected. I have boiled it, scrubbed it with hot water and Dawn detergent, degreased it with acetone, and tried just about everything that has been suggested with no luck. It makes bullets but it will NOT make good bullets. 
My theory is that small particles of zinc have gotten into the pores of the aluminum mold and are keeping the mold from making good bullets. If so, perhaps I could use a reverse-electroplating process to remove the zinc. Another option I have not tried is an ultrasonic cleaner. My friend had one but the instructions said to not use to clean aluminum items. Someone said there is an ultrasonic cleaner that can be used with aluminum, maybe that would help. If anyone can help me out I would appreciate it. I have bought replacement molds but I hate to give up on this one. 
thanks!
Joe S

The concept of 'pores' in metal, other than castings, is just nonsense in my opinion. 'Inclusions', garbage that made it through the rolling or extrusion process, is also a potential problem.

Zinc, being an alloying element in 7075, it seems more reasonable it's altered the chemistry of the surface of the mold. Why that would screw up the casting of bullets, and how to 'un'-alloy it, is 'above my pay grade'.

Boring it out for a larger bullet might be the only practical solution.

If smoking the mould and using hotter lead and tin doesn't work I would just buy a new mould. Aluminum moulds are cheaper than is all the trouble to do anything else.