The sturdier and heavier ( not always mutually inclusive) is your workbench, the better. If your bench is light or flimsy, it will move when you torque or whack the action wrench. The energy that should be going to break the barrel loose will dissipate into moving the bench. Basically, massiveness and immobilization of your vise are your friends in this situation.
Edit: A Sherman tank, D-8 Cat, or anything you have laying around that size would be the optimum mointing platform for your vise.


Kroil is good stuff and helps with this.
Not all people are haters of old slow twist barrels, so they are not super valuable, but worthless is a strong word.