I have bought a 8-cavity .22 cal aluminium mold from MP mold and started doing some casting last week. Upon opening the mold, the slugs always drop out by themselves but the lead mass on top of the sprue plate always stays there and I had to pull it out by using a piler. In all youtube videos on bullet casting I have watched, that piece of lead always drops out by itself. May I know how it is achieved ? I prep the mold by coating the cavity with carbon but I have not done anything to the sprue plate except for lubricating the pivot. should I coat the spruce plate with carbon as well to help releasing ?