What am I missing?

[GunnyMack]

Hollow base mould not filling out. Specifically the Lyman 20 ga pellet slug mould.
Running my Lee pot at about 4.5 on the dial(should be plenty hot?). The mould on top of pot for about 20minutes to warm. Pour a slug, let it sit in the mould to transfer heat, knock it loose, repeat multiple times. I'm still getting more culls than good pours.
What am I missing?
More heat?
Then the sprue plate screw wouldn't stay tight. Then the skirt plug retaining screw fell out of the mould, I think the threads are gone...

[Bronco]

I am no expert ! I think I would try a little more heat or add a little tin OR both!
I put my mold on a gas stove or a hot plate for a little while. Putting it on the pot took forever and so long to bring the mold up to temperature... like twenty times with rejects to get it hot.
John

[GunnyMack]

I was thinking Tin, I have it .
I will try heating on a camp stove or propane torch next time. Also going to dial up the pot.
Thanks for your thoughts!