I find 4 cavity brass too heavy. I like brass molds as I have several but limit them to 2 cavity. I only purchase iron or steel molds nowadays when they are vintage Lyman, RCBS, or my favorite iron mold, Saeco. If I need a 4 cavity mold, aluminum gets the nod. They all cast different depending on material, size of block, number of cavities and size of bullet. All will produce excellent bullets. I do preheat on a hot plate and usually keep the first bullet cast.