Ah... Easy way out: A 1916 Spanish Mauser with something massively wrong with the locking lugs in the receiver. I attempted to remove the barrel to investigate (and save the barrel if the receiver was junk). No luck.
I had a gunsmith try to pull the barrel. No luck.
I had another gunsmith use his over-kill hydraulic barrel vise to try to pull the barrel. No luck.
I said, 'screw it, get the torch', and we hit that stubborn SOB with heat, a pipe wrench, and cheater bars on both the pipe wrench and action wrench. No luck.