Just thinking out loud here- I wonder if maybe the different cooling rates of those two big bullets of vastly different weight would have had an effect on the final hardness? Makes sense to me, but I could be wrong.
I do not know much but that was my thought as well.
The 300s cooled quick and I could inspect them pretty fast. The 500s I had to weight quite a while before I could inspect them.
I traded off on the molding first one then the other to give the 500s time to stiffen up before I dumped them.
