Heat the molds before pouring.
The easiest way is to pour a few runs without hooks, put the lead back into the pot.
Smoking the molds with a candle will help the lead flow too.
Look into this stuff before you play with scalding hot metal.
We are here to help, but there is a VAST amount of information online.
Good luck, and cheers mate.
MAKE IT FUNKY ON THE ONE.