I started casting with two molds at once and placing the mold on a hot plate after filling the cavities with lead. So I fill two molds, then I empty two molds, repeat. The temperature of the hot plate is just what was needed for a good preheat.
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The 2nd biggest plus is that my sprue cuts are crazy consistent. The sprue and mold never get so cold that the sprue is difficult to cut, but they cool down plenty fast that I’m not wiping lead across the top of the mold when I open the sprue plate. The sprue cut is not perfectly flat - it does tear out some lead (92-2-2 alloy), but that might-could be fixed by lowering the hot plate temperature.
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The 1st and obvious plus is that my casting is very fast. I’m at roughly 300 boolits per hour (two 5-cavity molds) now and I’m not moving fast. I could actually do this with three molds and get around 400-500 per hour if I moved fast.
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Also, I accidentally left two molds filled for about 5 minutes as I was shutting down my pot and fluxing the oxides. The sprue cuts were the same as all others, and it was not difficult to cut.