Ive been pouring sinkers for several years now. In doing so I've found that the cone shaped "entry holes" in the smaller do it molds restrict lead flow and plug up if the mold isn't perfectly warmed up. I took a hand held wheel grinder and touched up the smallest most "necked down" area at the entry point of the mold making the hole a little bigger. You don't need to go crazy or it makes it tough to get the excess broke off after cool down but a little don't hurt any. The lead flows into the mold faster this way thus not plugging the entry hole if your mold isn't perfectly warmed up. I have done this to all of my molds from 1/2 all the way up to 5 oz. hope this helps some of you guys out. Most importantly be safe when working around this hot stuff!