Yondering, I understand the shortcomings of that very simplified test. But, it does give an idea of the question in hand. Personally, I was not too interested in the process because I ultimately want to use my PC'ed bullets for hunting and want them soft enough to expand reliably. I'm still playing with developing a good alloy for that purpose. No water quenching for me! So far, the unquenched bullets have shot very well indeed.
I may be able to help you with that, since I have spent a lot of time studying and experimenting how to achieve the same goal. What bullet are you using, and what is the meplat diameter, and what velocity? Also to start with, what alloy are you using right now?
Reliable expansion with either hollow point or flat point bullets is fairly easy to obtain with cast bullets, if you balance alloy, meplat diameter vs bullet size/shape, and velocity.
