As usual, I go back to what that wise old Veral Smith (he's younger than I am) has to say about most things pertaining to cast bullets. He says his LBT Blue melts at about 220 degrees. He recommends melting it and pouring it into the Star.
I bought a Pyrex measuring cup that holds a pint. Cut a stick of LBT Blue into chunks about an inch long. Drop them in the measuring cup and put it in the oven at about 250 degrees for a few minutes. When it has melted, pour it into the Star machine.
No more trapped air problems.