Firing .311 bullets in a .308 bore?
In the 7.62X39, esp in the Mini-30 I've read knowledgeable writers say it wouldn't necessarily be dangerous, but could with enough rounds wear-out the bore more quickly. In a higher pressure round, I would rethink this scenario..
As for the adapters made by Ace Dube from McAce in Alaska, I would use one in an emergency or survival situation. What exactly would I describe as an emergency or survival situation? To me such a scenario might be a real full-blown depression where ammo was scarce and expensive (like the one in 1929), or if ammo was outlawed, or through some fluke I didn't have enough ammo to shoot for my .308 Survivor and I had access to some 7.62X39 rounds and "needed" to shoot them now!. In such a case I would limit my shooting to what was necessary and only as far away as the shots had to be.
I would not expect great accuracy.
As for the .308W in a .30/06 chamber, as long as the adapter worked like it was designed to I think it would be fine - functionally, although accuracy might stink.