I just cast a batch of 45-70 using the lee 459-405-hb and since it casts nose up, the sprue plate cuts off at the nose. I'm opening the sprue as soon as the sprue pour "frosts". At this temp, the lead is still easily crumbled but not still molten. I get a fairly rough nose. How do I go about getting a smoother nose? Do I open the sprue sooner and let it smear a tad or wait until it is a bit harder so it "cuts" it more cleanly?