I am using once fired LC 7.62 brass. It was deprimed with a Lee universal and then pin tumbled.
To resize I was using a RCBS small base die and imperial sizing lube. I was meeting firm resistance at the base, but that was expected as this is likely machine gun brass. What surprised me was that on occasion on the upstroke I would either partially or totally rip off the entire neck. It is very tough getting a whole neck removed. On the last attempt I broke the threaded rod.
I have loaded a lot of LC brass and never had this problem. Suggestions?