I recently purchased a Lee single cavity mold 459-405-HB to cast a 405 grain hollow base bullet for my Springfield .45-70 Trapdoor Carbine. I cast a hundred bullets using a RotoMetals 20:1 alloy at 725 degrees F and they came out looking pretty good. But, I weighed them and they were consistent at 388 grains. I tried the tech at Lee and they said I needed to cast at 800 degrees. I tried again and it did increase to 390 grains. I called Lee again and asked why I could not get 405 grains as they advertised. They said their molds were based on a 10:1 alloy and since I was using a harder alloy my bullets would weigh lighter. I tried to explain to him that I was using a 20:1 alloy which is not harder than 10:1 and by their logic my bullets should weigh more than 405. I also told him their 10:1 alloy has a hardness of about 11 and the 20:1 alloy I am using has a hardness of about 10. He still says I am using a harder alloy and will not get the advertised 405 grains unless I use a 10:1 alloy. Can someone here please help me understand what I am missing???? I think the Lee tech does not understand alloy hardness. Also, anyone else used this Lee mold and how to get to 405 grains? Heat higher than 800 degrees? Thanks for any help!!