I also have a long history of bullet casting. It goes back to my youth when I couldn't afford to buy bullets.

I agree you want your alloy hot, and if using pure lead you need more heat. My casting has been both with wheelweights and with pure lead.

My experience is mostly with iron moulds, but I have used aluminum some.

I have a method I use when I cast, which you might find helpful. I always work two moulds. I fill one and carefully set it aside. Then I fill the second and set it aside. Then picking up the first mould I break it open, re-fill it, and set it aside. Then to the second mould, etc. etc., alternating back and forth. This method increases your production to almost double what can be done with one mould only, and it serves to maintain correct and even mould temperature all the while.

Try my method, and you will have good results.

Curl