You can overheat plastic hulls. When I first started using spinning mandrills turned them in a drill press hull clamped in a vise. Same rig I rolled crimped with. Clamped you don’t have any feel for heat, over heat the hull curls inward and ruined. Now I spin the mandrel horizontal in my lathe slower than the slowest drill press speed. Hand pushed on you can feel the heat and remove the hull when it gets warm leaving a fresh round mouth sized to suit.
Should say this additional loading step only useful with hulls that must be cut or are expensive. Several steps in cutting and skiving 10 G hulls and most times must be purchased, worth the effort to make them last.
William
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