Could HMS Warrior's guns penetrate USS Monitor's armour?
Short answerEventually, yes, but Monitor's guns could also penetrate Warrior, so tactical position and time under fire would matter.
NotesWarrior’s guns could eventually penetrate Monitor’s protection, and Monitor’s heavy guns could likewise penetrate Warrior. Neither armour scheme offered absolute immunity. Differences in speed, range control, sea room, and exposure time remain central to deciding which ship could bring effective fire to bear. This brief answer complements the longer tactical comparison without claiming a quick or guaranteed penetration for either side.