Quick answer to your question. Very little.

Shock is transmitted almost immediately from the receiver to the wood, and then to you.

Wood shrinks a bit as it ages. That can create gaps where the receiver meets the wood, reducing the load bearing surface and concentrating the recoil on an ever decreasing bit of wood. This is exacerbated by poor care over the decades, particularly the common “oil soaked” head of the stock. The oil further weakens the wood.

No one should ever ship a two piece gun fully assembled. ALWAYS break them down.

I’ve shipped lots of old guns. I pack them like they are valuable antiques. Which they are. I’ve never had a problem. Not saying I won’t but I sure take steps to make sure I don’t. Too many shippers of guns pack them badly.