Like it says, its stuck, looks to quite rusted. Stop collar threads have a good ring of a red rust. As well as looking under the primer seater on the bullet seater it has rust in it. I don't really want to use a punch from the other end to punch it out and risk damaging the bullet seater. I will probably douse it in penetrating oil over night, and try to twist it back and forth getting the oil in there, until loosens up. Wish me luck!