You mean using z-levels, construction, vehicle/furniture, goo canisters, zombies or…?[/quote]
Well, yeah, I did forget to mention leaving a pile of zombie corpses in front of the door, opening it, then staying the reality bubble until the zombies soak all the bullets, but that takes forever. Goo canisters could maybe do it, too, but you’d need a LOT of them.
And no, it’s not just digging down and tunneling in - getting the stuff together to dig or mine stairs is a pain. Easy to do, though, if you’ve got what it takes…