I was casting some bullets the other day and came across this trick, which BTW I have never read about.
I was casting some keith style 44's; the ones with the square lube groove. These are notorious for sticking in the mould.
Instead of opening the mould then tapping the handles to get the bullets to drop, I tapped the mould open - After cutting the sprue I lightly tapped on the mould handle to get the mould to pop open. When the mould opened, the bullets fell right out, nicely, everytime. Try this. It works great.

Max; Also try smoking the inside of your mould a little,that helps too. derf