Digging downstairs would would require more tools than just the jackhammer*. Collapsing ceilings is not REMOTELY dependable, and it would almost certainly expose you to their fire first, anyway.
*technically, my way also requires some other resources, but they are something everyone generally uses/carries anyway.[/quote]
serwers and subway are too far to mine tunell with anything[/quote]
Oh, once in a while, you can find a bunker quite close to a sewer or subway (or even a lab), but that’s certainly not dependable.
My way works on every bunker, and it uses stuff that is abundant and very available.